Ayumu for me. He's the oldest and most masculine looking (I'm 30, so guys that are or look like little boys aren't appealing to me), and I can relate with his bio as I do freelance journalism myself. Second favorite would be Ryuusei, more so for the description itself than his appearance (speaking of which, what the heck is up with the elf ears?).
But anything can change once I play the game.
"I am sexy minority. OH! NO! I wanna be a sexy terminator. Sexy will never die. AH~~~~~!"
Shirabe is my current favorite guy too, but Urabe, Mitarashi, and Shidou are all appealing to me as well.
It's so unusual to me that I like a majority of the guys available, because it's usually just one or two that pique my interest, or I prefer the non-datable NPCs. (Shinpachi...) I'm very pleased with the selection of men in this game.
Currently Playing: Animal Crossing: New Leaf (3DS) Looking for Ankha, Zucker & Phil in New Leaf, PM me! (Currently on hold, town full.)