Well, pretty much any cool celebrity. I had the ultimate awesomeness of meeting my idol Angus Young at an IHOP after a show in 2001. It was the Stiff Upper Lip tour. I got there, and saw him and nearly pissed myself! It was him and Malcolm Young. After I finally got the courage to talk, we chatted for about a half hour (It was mainly me talking about how much I worship him and his guitar playing). But after a while, he grabbed two Gibson SG's out of his rent-a-car and I showed him how much I knew of their songs, which is a lot. And after a while (By now it was probably 2 AM) we finally left...reluctantly...but I had a ton of autographs!
I also had the...ahem...convenience of meeting Bam Margera. If you don't know him, he was in Jackass and was the star in the MTV show Viva La Bam. And me, being a big Jackass fan, went up to him and ask for an autograph, he basically just said "F*** off kid." Yeah, not my favorite moment in meeting-a-celebrity times. Eh, I thought it would have been cool. But I saw him once or twice more, didn't even bother trying to talk to him. I saw him at some skate parks back when I used to skateboard. He only lives about 10 minutes from my house.
I was close to meeting Slash at a Velvet Revolver concert. But he got swarmed by a crowd and ended up leaving. Eh, I was close. I probably would have pissed him off, mainly because I really know him from GnR, and barely any of his music from Velvet Revolver.