I realize that this is kind of an odd question, but I like asking it because it shows how secure people are with themselves. I think it's an honest question that shouldn't be particularly offending to anyone, since it is a "what if" question. That, and I just like knowing.
I'd have to say, off the top of my head, Robert Downey Jr., Johnny Depp, Michael Buble, Daniel Craig, and David Tennant.
Who would you go gay for? You know, if you're comfortable saying so.