Five Acts - My List
1.) Protectiveness/Possessiveness. There's something very sexily adorable about one person wanting to have and protect the person they love. I also like when there's a bit of tension in the relationship about this.
2.) Double-penetration. Yum. I have no real explanation to go with this one: it's just hot. In the case of M/M/F threesomes, you are more than encouraged to play around with pegging with this kink too. ;)
3.) Taking it slow. As hot as it is when characters jump into bed together, I love the tension that comes when they decide not to do that - whether it's because the circumstances aren't right, they don't feel ready, or there's a big stinking supernatural curse that means they can't get fleshy with one another quite yet.
4.) Tattoos. I have such a thing for ink, especially on characters where you (and their partner) might not expect it.
5.) Sex pollen. Or "aliens made them do it" or sex magic or having to kiss/more to keep their cover on a crazy undercover job or any kind of wacky sex adventure, to be honest. Silliness and sexiness are good bed partners.
Fandoms/Pairings:
Angel/Buffy: Angel/Doyle, Angel/Doyle/Wesley.
Being Human: Annie/George, Annie/George/Mitchell, Daisy/George/Ivan, George/Ivan, George/Mitchell.
Community: Abed/Troy, Annie/Jeff, Annie/Britta, Britta/Jeff
Crossovers: Adam Monroe/John Winchester (Heroes/Supernatural), Charlie/Oz (Lost/Buffy), Doyle/Anyone (Angel/Any other fandom), Esau/Lucifer (Lost/Supernatural), Eleven/Castiel (Doctor Who/Supernatural).
Doctor Who/Torchwood: Amy/Eleven/Rory (and all combinations thereof), Donna/Ten, Jack/Mickey, Martha/Toshiko, Donna/Martha/Amy, Owen/Rhys.
Dollhouse: Alpha/Echo, Alpha/Victor, Topher/Victor.
Fringe: Any combination of Astrid/Charlie/Olivia, Astrid/Peter, Charlie/Peter.
Glee: Finn/Kurt, Sue/Will, Mercedes/Quinn.
Heroes: Adam/Elle/Monica, Adam/Monica, Elle/Monica.
Inception: Cobb/Anyone (I'd love Cobb bottoming if you write anything higher-rated with him), Ariadne/Yusuf, Eames/Yusuf.
Leverage: Eliot/Hardison.
Lost: Ana Lucia/Michael, Anyone/Charlie, Anyone/Frank, Claire/Juliet, Claire/Kate, Claire/Jack, Daniel/Juliet, Daniel/Frank, Daniel/Miles, Esau/Jacob, Frank/Miles/Richard, Jin/Sawyer, Kate/Kevin, Kate/Sayid, Kevin/Sawyer, Scott/Steve.
Luther: Alice/Anyone.
Merlin: Gwen/Lancelot, Gwen/Lancelot/Merlin, Gwen/Morgana, Lancelot/Leon, Lancelot/Merlin, Lancelot/Uther, Merlin/Leon, Lady Vivian/Anyone, Gwaine/Merlin.
Misfits Simon/Anyone.
Primeval: Becker/Connor.
Sherlock: John/Anyone, Anthea/Molly.
Sherlock Holmes: Holmes/Watson.
Star Trek: Anyone/Chekov, especially Chekov/Kirk/McCoy.
Supernatural: Castiel/Lucifer, Lucifer/War, Gabriel/Lucifer, Castiel/Gabriel, Castiel/Gabriel/Lucifer, Castiel/Michael, Castiel/Balthazar, John/Any angel, Bobby/John.
The Walking Dead: Rick/Shane, Lori/Rick/Shane.
True Blood: Eric/Lafayette, Lafayette/Jesus, Eric/Lafayette/Jesus, Russell/Talbot, Tara/Sookie, Tara/Franklin, Jessica/Hoyt, Hoyt/Anyone.
I also love OT3s and crossover pairings featuring any of the characters above (especially John Winchester, who goes perfectly with everyone.), but I would go on forever if I tried to list every possible combination!