I do ship Steve/Tony, like fedex but I can see why people wouldn't. But in the Avengers fandom over in AO3 they do have tags, because I know that Darcy/Loki is a popular pairing, as well as Coulson and Clint (I... don't get that one, but okay). There's a lot of Bucky/Steve as well, so you cannae go wrong with that. I think postcardmystery over in LJ has Steve/Bucky and rarepair fic for your very needs. AO3 has lots of stuff too.