Werewolf in the Fold (Star Trek/Teen Wolf, ~5000 words)
When the two survivors (and only suspects) of a colony massacre are brought aboard the Enterprise for transport to their trials, Ensign McCall suspects there's a bigger mystery behind it all - and not just the mystery of the younger suspect, the captivating Allison Argent, who has yet to say a word since the massacre.
Even though it's the longest
Edit: And the fic written for me is out! \o/
Once Was Quiet (Firefly/Stargate SG-1, ~4000 words)
Nobody had heard from the colony for a while, but now business brings them there.
It's got incredibly good character voices for two fandoms with (to my mind) a number of characters that are both distinct and difficult to write. That alone would make it impressive, but it also does a really excellent job meshing these two universes together.