I'd have to agree with not having scripted jokes in your routine. I think there are very few staples that one can rely on........however......that's not to say I don't have my one joke that never fails to get a laugh.
PERFORM WITH CAUTION, VIEWER DISCRETION ADVISED.
When performing Prophet, I say....."What can you buy with 5$ nowadays? Not much right? I mean I can buy _____ (spectator's name) for a night, but that ain't saying much..."


Or you can substitute "I can buy your girlfriend for a night...but that ain't worth much either..." etc. you can really get flexible with this one.
It's horrible...BUT it's funny and gets me on an equal level with the spectators. Someone they can relate to as being an ordinary guy, just like them. That has to be my favorite part about performing, getting to meet people. Ofcourse, this might only work for the younger generation, but you only live once...so why not do it while you still can?
Lastly...this only works for an outgoing/funny persona. If the performance is serious ie: David Blaine....people won't take it too well.
Enjoy!
-Andrei Jikh