Im always impressed by a guy who is a gentleman. I mean I am impressed by guys who are good at music, sports, whatever. But not everyone has those talents, but anyone can be a gentleman. Just little things, holding open the door for a girl, telling her she looks nice, acting sincerely intersted in what she's sasying. Things like that always impress me. And the girl doesn't have to even be your girlfriend to do those things to. Even if you aren't funny or you have no sense of style or you can't play a sport you can be a gentleman, and that always impresses girls.
Sense of humor! And not a stupid sense of humor but actually witty. Also, a good (similar, varied) taste in music is good, and dressing well (ok, MY idea of well anyway - think Urban Outfitters haha) is a plus too. Chivalry is nice. But just the general personality.
The major thing that impresses me is humor in a guy, along with witt. If a guy can keep up with my weird sense of humor, its impressive. Another thing that impresses me is a guy who can impress older women. If older women, like mothers or grandmothers, like him, he's probably a great guy. And animals, if a guy is constantly being attacked by parrots or something, its not so impressive, but if he can calm down my maniac of a poodle, he's impressed me. I'm easily impressed btw