SGA, Sheppard/Todd:
"Sometimes a Great Notion" by
curia_regis (PG-13) -- There is an old Wraith saying and it goes something like this: "Humans are always food, and occasionally entertainment, but never worthy of trust."
Merlin, Arthur/Merlin:
"His Own Hand" by Crazypaving (NC-17) -- In which Merlin is punished for saving his life for the thousandth uncredited time, and arguing with Uther is the stupidest thing Arthur's done until the next thing.
Generation Kill, Brad/Nate:
"what you are and who i'll be for you" by
lickingbeads (R) -- Even without DADT and the small matter of Nate's own preferences, the line between grunts and CO's is there for a reason, and it's uncrossable.
Greek Mythology, Ares/Apollo:
"Sex Tsunami (Or, How Apollo Learned To Stop Worrying And Love The Force Of Nature That Is Ares)" by Brenda (PG-13) -- Apollo is used to Ares ruining his good time. Luckily, he has a way of making up for it.