The Perfect Prank

Okay So Band is cool, don't know if i've said that before or not but i have to admit that at times it can be a little boring and needs some excitement to make it cool again. Last year we began pranking some people in the band with vaired sucess, it was fun and gave us something extra to do. Anyway, our classic prank from last year has been retired and we need a new prank. I'm looking for something that is can be done at a low cost, not make people too mad, and most importantly something that isn't illegial or something that might make me feel guilty or like i did something horrible.

The best i've come up with so far is spraying people with water guns, so yeah pretty sure anything you suggest is better then what i have.

Spraying with water guns?
What the &$%# kinda pussy prank is that? Sheesh...