I don't mind Prison Pete or really any of the others, EXCEPT the Maze. Very frustrating and by the time I FINALLY get to the center, I get what is most likely the worst reward possible.
Hated that maze. Would kill my bot and I would have to go and do it myself. Still, I have gotten some good stuff though as it is pretty easy to do once you get the hang of it. All the others I can handle.
Maze due to the unbelievable time it takes to complete when your not paying attention.
Pinball because, well, its boring.
Evil twin claw one is also bad if you have lag (makes it very hard to pickup and get timing right).
Also the gravedigger is plain boring.