There are lot's I know. Ok, the first one I know is a peeing brute in the level the covenant. I'll do my best to tell you but all you have to do is beat the whole level on any difficulty.(Recommended:Normal). Then after you beat the level, go on theater, and once you've entered the covenant's place just go forward, and leave it on pause once you've entered the house, and you should at some point find a brute facing a corner with his hands down. That's one of them but another one is masterchief flexing. So go on forge and go to the level "Last
reasort", then once you're in the level go into the oracle and fly over to the beach.Once you're there, Turn back into the human and stand on top of the warthog FACING THE OCEAN!!!!! Once you've done that, go into the oracle and and try to fly up straight, then, look left and there you have it, the chief flexing. Oh yeah, he's a cloud!!!!