Inspired by the finale of Supernatural, I started making a list of my top flail-inducing season/series finales. I started out coming up with ten, then that went to fifteen, and eventually I stopped at eighteen. Mainly because I couldn't think of two more.
Needless to say, here there be spoilers. And I'm sure I'm forgetting some trauma.
1.
Buffy the Vampire Slayer, Season 2 ("Becoming, Part Two"): I was literally flailing and running around in circles after that one. I couldn't believe that Willow restored Angel's soul -- and Buffy still had to send him to hell. The death of Buffy in S5 didn't nearly affect me so much because I knew she'd be back. Angel, I couldn't be so sure about.
2.
Nip/Tuck, Season 2 ("Joan Rivers"): Sean sets up an ambush for the Carver . . . who attacks Christian instead. COMMENCE. FLAILING. I knew Christian wouldn't die, but there was the risk of serious injury and rape.
3.
Battlestar Galactica, Season 1 ("Kobol's Last Gleaming, Part 2"): HOLY CRAP BOOMER SHOT ADAMA OMG OMG OMG. That about sums up my level of coherence.
4.
Babylon 5, Season 3 ("Z'ha'dum"): "Finally, I heard what you said when I left. I want you to know, I love you Delenn. Goodbye." Jump? JUMP?! What do you mean, JUMP???
5.
Battlestar Galactica, Season 2 ("Lay Down Your Burdens, Part 2"): The Year in Baltar's Hair. Seriously, whammo, a year's passed by and the Cylons invade and the Galactica flees and leaves thousands of people stranded on New Caprica as the Cylons march into town. Eee!
6.
Star Trek: The Next Generation, Season 3 ("The Best of Both Worlds, Part 1"): "I am Locutus of Borg. Resistance is futile. Your life, as it has been, is over. From this time forward, you will service us." Ho. Lee. Fuck.
7.
CSI, Season 7 ("Living Doll"): *&^%$# Sara is left pinned under a car in the middle of the desert, with thunderstorms coming in (and thus a high risk of flash flooding).
8.
Farscape, Season 4 ("Bad Timing"): End of the series, Aeyrn's pregnant, Crichton asks her to marry him, she accepts . . . and then they get blasted by a ship and turned into a pile of tiny crystals. WTF???
9.
Profiler, Season 3 ("Las Brisas"): Fake!Jack is on trial, confesses, and is convicted. Because the viewing audience is smarter than the VCTF, we have known he is not Jack since, oh, the beginning of the season. Sam is all "Yay, Jack is gone, I'm safe now" and goes off to spend some time alone in a cabin in the middle of nowhere. And, of course, Jack is waiting there to shoot Bailey and kidnap Sam. Whee! I mean Eeeeee!
10.
Supernatural, Season 1 ("Devil's Trap"): Fortunately I didn't have long to flail since I started watching SPN late, but still, Dean + Sam + John + twisted wreckage of the Impala? Eeek!
11.
Battlestar Galactica, Season 3 ("Crossroads, Part 2"): The Great Cylon Reveal. I was pretty much confused and WTFing over that one, but so far I'm enjoying the ride for S4. NEED MOAR NEKKID SAM.
12.
Heroes, Season 2 ("Powerless"): Nathan!!!
13.
Charmed, Season 3 ("All Hell Breaks Loose"): Phoebe in the Underworld, agreeing to remain to bring Piper back to life, the Source ordering her death and Cole's imprisonment, and, of course, Piper and Prue getting blown through a wall by Shax (aka Death by Alyssa).
14.
Supernatural, Season 3 ("No Rest For The Wicked"): Dean in hell with a meathook through his shoulder. Well, that can't be good.
15.
Farscape, Season 2 ("Die Me, Dichotomy"): Crichton gets taken over by the Scorpius chip and kills Aeryn. Oh, and if that wasn't enough, Scorpius shows up and takes the chip, leaving John helpless on the operating table with his brain exposed and the doctor incapacitated. *flails*
16.
Angel, Season 5 ("Not Fade Away"): Dear Joss. I hate you.
17.
Melrose Place, Season 3 ("The Big Bang Theory (Part 2)"): Kimberly blows up Melrose Place. Hell. Yeah.
18.
Soap, Season 4 (Series finale): I love this show. But it ended rather abruptly and the danging threads NEVER got resolved. Chester's about to kill Danny and Chester's second wife when he catches them in bed together. Burt's walking into a trap. And Jessica is about to be executed by a firing squad in South America. Well, there was a tiny bit of resolution when Jessica's ghost showed up on Benson and told him she wasn't dead; she was in a coma.