Comment and I'll:
1 - Tell you why I friended you.
2 - Associate you with something - fandom, a song, a colour, a photo, a sexual position, etc. (Or, not)
3 - Tell you something I like about you.
4 - Tell you a memory I have of you.
5 - Associate you with a character/pairing.
6 - Ask something I've always wanted to know about you.
7 - Tell you my favorite user pic of yours.
8 - In return, you must post this in your LJ.