While it wasn't as critical a success as its forebear "The sixth sense" I liked how a main character turned out to be the bad guy all along.

I see that two FBI partner's start out and one turns out to be the bad guy all along. This would then reveal the irony of everything the bad guy said on the second viewing. The psychological make up of this guy, his fascination with money - house prices, his stock portfolio; his fascination with success, fame and fast cars. Things that justify the sellout that he perpetrates on family and friends.

Something to try out.

Fight club was also a good example of the genre - what you see through the main characters eyes is reality and every other character to screwed in the head. But once you find out to the contrary it flips the whole movie on its head. Brilliant for repeat viewing.