I really like straight guys on gay guys or, when the tables are turned, gay guys on straight. I've never found the straight-on-straight all that hot; it usually looks like both people are pained to be there.
And when one of the two straight guys does like it, I can't shake the feeling that he's really pretending to be straight. Reading some of the behind the scenes stuff here, I think that's usually the case. There's probably a good amount of money to be made on a "straight-vs.-gay" site, too. But that's another post.
I also like kissing. And the moaning. And the frantic, with-it fucking. And when a guy swallows another guy's load. Haaaaawwwwwttttt!