Stargate (SG1/SGA), O'Neill/McKay. I've seen a few good Slave!fics with Shepard getting ownership of McKay, and something along the same lines with Jack would be cool. Or Rodney sticks around the SGC after the events of 48 Hours to fix Carter's bad protocols, and Jack slowly and unwillingly gets to like him. (Or you know, doesn't and there's some darkfic after Daniel dies and Jack gets tortured by Ba'al.)