So, the ones I've come up with so far:
An AU set in the BSG universe.
An AU where the guys are an American version of Torchwood.
Something or other that involves James Bond. Ezra and James playing cards in some swanky casino.
I'd still like to see either a modern day or OW crossover with Forever Knight. Now that, I might write some day.
An AU set in the PotC universe. Buck and Jack Sparrow on the town in Tortuga.
Okay, I'll stop now!
Oh, and how could I forget the Chuck/M7 ATF cross I want?
Now I'm done!