Note: Hawkeye isn't the sort to dislike anyone. She's exceedingly patience and understanding so getting her to dislike you personally is hard. At best she is wary of people, or considers them a threat but won't hate them.
Hawkeye tries to meet everyone, but not all that many leave impressions on her thus this list consists only of the ones she has any specific notes on.
Honshou Chizuru - Lesbian. ...fifteen year old girl hitting on her. Yeah, whut.
Ishida Uryuu - Notes that he's very standoffish, even if she hadn't been warned she would've known by his manner that he picks fights often.
Bart Allen - Fond of him, very cute, is impressed by his ability to catch bullets
Huang Yue Ying - Wary, doubt that the claims that Miss Huang set up her death are entirely unprecidented, but doesn't intend to persue the matter. Finds her overall friendly though.
Alphonse Elric - Hawkeye loves Al like... an aunt? She immediately disapproved of him being on the council not because she doubts his ability, but because he's still just a young boy and that kind of position and the resulting stress is pointless to put upon him when there are plenty of other qualified people to take over.
Edward Elric - Pretty much the same as with AL, except that she respects the choices he's made to get where he is and is thus more inclined to treat him as an adult.
Winry Rockbell - Friends! Canonically! Pleasent relationship but they really don't talk to each other a whole lot in the manga. Might change in camp.
Sagara Sousuke - Even more militant than her, impressive
Izumi Shion - ....okay. Where to start with Mr. Izumi.
First of all, there were a lot of events that lead up to Hawkeye meeting Izumi. Most of them are recorded
here. The short version is that Izumi is fucking nuts and he likes to hurt people, and the people he went after with Mal and Robert, two campers Hawkeye is somewhat close to. Mal was tortured, Robert was shot and later stabbed. I'm blaming the fact that she was slow to act on the fact that it took her a while to have the idea she finally got, due to the fact that she's not used to concepts like 'save points'.
Anyway, what happened was that after Robert was stabbed by Izumi Hawkeye talked to him. She explained that the moogles would no longer 'save his game', and that his previous date had been released. Now he couldn't treat his life so arbitarily, and no matter how you look at it Izumi was making enemies of Robert, Ueki, Hawkeye, Mal and Roy. All of them dangerous in their own right. She pointed out that if Izumi did decide to get himself killed, it was likely the camp would take a while to bring him back, and might return him to life as something... less than alive. Say a zombie or a ghost.
Then she shot him in the knee.
Then she put her gun away and helped him to the hospital where he was allowed to be tended, albeit not the doctor's greatest ability.
Hawkeye does not hesitate to kill people. She killed children during the Ishibal Conflict, she could sure as hell kill a seventeen year old psychopath like Izumi and sleep well at night. However, she is a stratigist, she's goal oriented and not the sort to let arbitary revenge get in the way of the greater goal. In this case the greater goal is that Izumi stop trying to hurt people, since she cannot kill him permanately, killing him semi-permanately when he may just come back and make it his Mission In Life to kill them all as slowly as possible seems like a bad idea. Instead she incapitated him, making him as small a threat as possible, she also offered him a 'out' if he wanted to take it. The shot in the knee is the only time Hawkeye will ever attack Izumi unless he continues his threats, but she made it clear she would shoot out his other knee if he did continue. Basically, she never intends to kill Izumi, a fact that confuses him. She has stated plainly that she will, however, continue to shoot him in key areas to keep him direly incapitated if he persists in acting as a threat, eventually Izumi will be physically fucked up he'll have to take his own life and risk dealing with the results.
She's done her very best to make continuing to hurt people she cares about as undesirable as possible, and it as, for the moment, succeeded.
Nishi Jouichirou - She was warned about hiim by Ari, thus will keep an eye on him when she meets him officially. She has met Nishi but he refused to give her his name, but Ishida came by later and made threatening poses she didn't miss so she rather suspects Nishi is Nishi.
Lunamaria Hawke - First person to hurt Hawkeye's brain when she mentioned space colonies and thought Hawkeye was joking when she said her world hadn't even achieved in atmosphere flight. Still, she likes Lunamaria quite a bit, as she does pretty much anyone from ZAFT. Maternal instincts whut.
Shinn Asuka - First kid Hawkeye adopted. She and Shinn have long talks about the ethics and gray areas of war, in which he emos and she is as calm as ever. She's very fond of Shinn, and doesn't seek to tell him he was wrong in his choices he's made in life so much to get him to understand that war is a horrible necessity, but it's not the only choice and it's not justified.
Yzak Jule - The only ZAFT member she calls by rank (since he's the only one that has one, apparently), Hawkeye is fond of Commander Jule and treats him with the respect she gives any military personal, regardless of his age, because he seems to want it that way. She's especially impressed that his "ZAFT HQ" is not a re-establishment of old wars, but rather a place that accepts any soldier from any side to train.
Tom Marvolo Riddle - Definitely a threat. Along with everyone else she's a little concerned that Edward got in over his head when he got involved with Mr. Riddle. However, Mustang has made it clear he intends to watch Riddle, so she's not immediately concerned.
Nishizono Tetora - Potential threat, with the way he waves around guns so casually. Will be watched.
Yakushi Kabuto - Calls himself a medical ninja, very polite and helpful. She's made a mental note to seek him out if there are any injuries.
Ari - Extremely fond. Ari's adorable and he loves Black Hayate like he's the best thing since sliced bread. Plus, Hawkeye's rather refreshed that there are kids here with normal reactions to guns. Namely not wanting go near them.
Ash Ketchum - Was well warned. However upon meeting Ash she finds him merely enthusiastic. Definitely a good potential for headache inducing, possibly even an Armstrong effect. But she'll still like him. ETA1: Was forced to pull out her gun when Ash went running around pantsless in Ari's body, this event combined with help from 'Officer Jenny' convinced Ash that she is a member of Team Rocket. Riza doesn't actually care but is getting a little exasperated.
Brock - Hits on her, but makes good riceballs.
Mizuno Ami - Though Miss Mizuno spent a while arguing with Hawkeye over the ethics of teaching kids to use guns, she left no real personal impression on Hawkeye. Though it's been noted that Miss Mizuno takes the safety of the campers seriously which is somewhat of a relief.
Anakin Skywalker - They discussed things about the barrier and Hawkeye's friends arriving and... I can't actually remember. He left a good impression on her though.
Azuma Kazuma - One of the few people that really amuses Hawkeye. Very cute kid and she's looking forward to see how her sending him to watch Roy works out.
Robert Haydn - A mystery to Hawkeye. He appears to be perfectly intelligenct yet somehow has no idea what sex is. Inspite of her rigid nature, Hawkeye isn't a prude and thinks that any boy by the age of fifteen should know what sex is, even if he hasn't experienced it himself. However, attempts to give him sex ed. merely resulted in Roy taking advantage of a chance to kiss the Captain, which mostly just makes Hawkeye sigh; she really thought the Captain would hold up longer. Anyway, Hawkeye is more concerned with Robert over a comment about his father intending to become God and wipe out humanity etc etc. Of course she assumes that the man was simply crazy, but she's worried on what effects this has had on Robert and intends to keep an eye on him incase he needs protecting from himself. Add: Robert and Hawkeye tend to be on somewhat unsteady terms lately. It doens't particular bother Hawkeye, she's quite used to children not 'getting' her. Her primary concern is always with his health, which unfortunately has been failing lately due to Izumi Shion's involvement, so she stepped in and resolved that issue. Otherwise they are talking less, partly because Hawkeye kind of... offset? Robert when she asked him about his world, and partly because the mun hasn't been around to play their interactions much lately.
Mello - They spoke when Mello was in Chisame's body and posted a poll regarding the reactions of the counsellors. They had a nice and very civil discussion about the reasons for those actions, possible better ways to handle things and future concerns. All in all he left a good impression on Hawkeye, though she senses that inspite of his words on the subject he is not... as sincere as he appears to be. Also he mentioned his rather violent relationship with his partner Near (and that he apparently belatedly replied to an old post regarding violence at the camp the player needs to go review) and Hawkeye pretty much immediately began to associate it as "one of those things" similar to how Ed throws things at Roy or Hawkeye herself threatens to shoot her co-workers.
Lu Meng - Hasn't really spoken with him, but has already noticed that a rivalry with himself and his men against Huang Yue Ying has caused problems. On one hand, she doesn't really fault him as in reading the posts he tried to put things behind them. On the other hand Lu Xun made a post regarding Ying possibly having killed Lu Meng in the past and that they were afraid she would try it again. In Hawkeye's mind the whole situation was handled incorrectly and subsequently spiraled out of control. As the commanding officer of his own forces, Lu Meng should have headed this off.
Malcom Reynolds - Likes Malcom quite a lot, actually. And she appreciates that he let go of his grudge against the military. She kinda tends to play with him, since she's so very serious it's pretty well impossible to tell when she's making a joke or not, especially since she'll never crack a smile or explain it. It leaves him dotting over her quite a bit which she finds secretly quite entertaining. ETA1: Has gotten into the habit of flirting idly with the Captain, mostly by way of poking fun at him and the Colonel. Hawkeye doesn't get crushes on people, but she does have an interest in him, and notes that the Colonel also trusts him which goes a long way with her. ETA2: Yeah, okay, they flirt quite a lot. Hawkeye's started being more honest with Mal. Hawkeye is used to the people who need to understand her doing so instinctually. Havoc and Roy can tell when she's joking, though her sense of humor offsets them anyway. Mal can't tell AT ALL, he just... stares at her. She finally let him in on a joke one day and the fact that she'd apparently had a very secretive sense of humor all along apparently tickled him.
Alex Louis Armstrong - Does anyone NOT like Armstrong?
Izumi Curtis - Despite that Izumi has offered to hurt Mustang, Hawkeye doesn't consider her much of a potential threat. No more than she does Edward. Still, Izumi didn't leave the greatest of impressions. Probably because while Hawkeye agrees the military is corrupt, she doesn't agree that any other form of government is necessarily better, at least not for the reasons Izumi listed. Hawkeye is a very pragmatic idealist, not the kid of idealist who hopes but one who does the dirty job to accomplish things. In her mind any government could be just as corrupt, that is simply the nature of governments. Thus her immediate concern is changing the leader of the government, not the structure of the government itself. There is also the fact that Izumi speaks badly against the military and... that's it. Hawkeye doesn't expect everyone to get involved in a covert war against the Fuhrer, but it did surprise her that Izumi continues to consider all members of the military 'bad guys' regardless of their goals.
Jean Havoc - Ironically Hawkeye and Havoc very little canon interaction. I think she interacts more with Fury than she does with Havoc. Still, she respects and cares for him and I'm secretly a Hawkeye/Havoc shipper so we'll see where they go >D
Maes Hughes - Oh god. I think, more than anything, Hughes represents something to Hawkeye. I'm sure they were what she would've called friends, but she wasn't the one torn appart by his death. As always she kept cool and collected, that is what Roy needs of her and no matter what Roy is always her primary concern. But Hughes plays a game with Roy as much as she does. While she is the stone, the defending walll, he is the... life. The family, the friend, the laughter. More than simply someone who was going to 'push Roy to the top' he was the one that made sure he remembered what made their fight worth it. More than just losing Hughes, Hawkeye was afraid that his death would hurt Roy in a way he would never recover from, and the smiling mask would become more and more just a mask. Suffice to say, nothing will hurt Hughes again, ever. For Roy's sake.
Roy Mustang - ...Ironically, I covered all of his in the character write up below. Suffice to say that Riza's life revolves entirely around Roy. The End.
Gilbert Dullindal - Potential threat, she's noticed concern about the campers regarding him. Notes that he's a politician to his marrow.
Tsunade - The mutual respect of awesome strong women. They plotted to do something about the council together. Riza respects Tsunade's strength and matter of factness, and subtly discusses controlling people who need direction with her.
Sha Gojyo - Permanately "Mr. Gojyo" currently just another tiresome guy that hits on her.
Nicholas D. Wolfwood - Nicholas... she likes him a lot. He's up there with the Captain and Shinn as far as new people she's fond of. He likes kids and is frank but apologetic about his nature. Genuinely means well while lamenting his emo-y past. Kindred spirit much? He's an interesting, funny guy and one that she can intimidate without even trying.