I have this problem where I do get hit on once in a while, but I remain completely oblivious to it until afterwords. My best story though that was for sure a girl hitting on me:
I started going to concerts a lot more lately, and half the time I go to them, a girl ends up chatting me up. So I was at a concert for a pop type band with a friend (who is a girl), just having a good time.
A crowd is a crowd, but I kept getting tapped on the shoulder so I turned around after a couple of times. The chick was trying to get my attention for whatever reason, but she was standing with some guy. I assumed they were friends, but she was asking me questions about the concert anyway, and then about whether the guy beside her looked like the guy on stage (he actually did look similar). I didn't think much of it though still. She's smiling, moving in a bit closer to me and whatnot, and she'd keep getting my attention every so often if I stopped talking to her to enjoy the concert. This girl was pretty damn hot too... a blonde slightly scenish chick with a nice body and everything...
Eventually she says "Hey, are you here yourself?" with a big smile on her face.
I responded with "No, I'm with her" pointing at my rediculously short friend in front of me. That's my brilliance shining right there. As if that wasn't enough to clue me in though, after I said that she just yelled in disappointment.
"DAMN IT!"
I then went back to enjoying the concert. 5 minutes or so later I finally clued in on what was going on, but I had lost her in the crowd at that point.
To this day I'm still kind of pissed at myself for not picking up on it until after (story of life), but at the same time I can't help but smile when I think of that time because that chick was legit hot, and that kind of stuff doesn't really happen to me.
Other then that, any time I get a hair cut, I get a lot of attention. Everyone at school noticed, and all the girls were telling me I liked hot. The attention was definitely nice, especially since almost all the girls in my class are attractive themselves.