People have already said the obvious ones his eyes, voice, and chest. (LOVE the hair!)
I have to add in there his handshis fingers are long and slender, so sexy. If you put him next to various cast members in any given movie he's been in, I'm willing to bet I would be able to identify his hands out of the rest simply based on them alone, lol.
His lips are nice too, and I'm a fan of his teeth/smile.
I don't put movie quotes in my signature.

I'm right there with you!! That chest of his is sooooooo sexy!!!
"When the chips are down these, uh, these civilized people . . . they'll eat each other."

His gorgeous piercing blue eyes, his voice and that yummy hairy chest! Man, that is such a turn on, all I wanna do is rub my hands over that chest..

Awh, yeah I love that Skyone interview!! So much fun, such great humor . . . ooh, theres another one. His humor does it for me, too. lol

Hahaha, I love how he says "roll with" in interviews, lol. Everything about him is just so sexy. Ever see his interview with SkyOne about season 6 of LOST?? Check it out on YouTube - it's fabulous!!
"When the chips are down these, uh, these civilized people . . . they'll eat each other."

Yep the eyes are a given!! You mentioned his voice; I love that too. So, Ill go with his laugh. Wow!! Tb68hat does it for me also. I always hope for at least one scene with that laugh. I can "roll with" Bish-Fiscuit's comments, too.

I am not a lady, but my favorite attribute is that he is literally pretty much a real life version of his character on Lost, Frank Lapidus. Does that even count as an attribute? I don't even beep care.