I tend to be more of a character person than an actor person, so I had to think about this one. For example, while I think Tony Stark is hot, RDJr in general doesn't do it for me. So if this had been four characters I lust after, you'd probably see a few different choices in some cases.
So here's my four
Peter Wingfield (Snagged the photo from pat_t. She took it last weekend, so it's fresh!)