Haha, I love threads like these! I definitely have a thing for:
Brynjolf - Seriously, you are right on. Dat accent, and hypnotic voice. Dat sex appeal. He's an intriguing character all around and I've really grown quite fond of him. I wish *so* badly he were marriageable, but hey. When I get the PC version and play with some mods, I'll see if there isn't a way to at least make him a follower. All your fault, Jers.
Marcurio - I have a thing for Imperial men as it is, and so it was mega bonus points for his destruction mage skills. One thing I have noticed: the Imperials have great eyes! He's my lovely husband in my main file. Had to happen.
Mercer Frey - I've just recently been able to spend time with him in game. He's actually my multi-purpose follower at the moment, haha. This is much to his annoyance, I can tell. He's been grumbling the whole time, especially when we go to Solitude or Whiterun. I love the sass, what can I say? ...Again, your fault, Jers.
Rune - One of my Thieves Guild brethren, he's one of the few true sweethearts I've run into. It's too bad he's not marriageable either; maybe with mods... But yeah, another adorable (and hot) Imperial FTW!
General Tullius - I should add him as well, there's something about him. Being a fan and student of Roman history, I can't help but see Julius Caesar when I look at him. Which is a good thing in my book.
This is who most immediately comes to mind - I'll revise as I think of more, haha.