Patrick Jane is actually psychic, but either he doesn't realize it, or the more interesting option: he's managed to convince himself that he isn't (possibly repressing knowledge of his true powers after his wife and daughter were killed because of them).  He's still using the powers, but he doesn't realize that he is, and he always has an answer about how he knows the things he knows (because he does know how to do it powerlessly), until one day...he doesn't, and he's forced to confront that knowledge.

Girl!Jane

Mentalist--I don't think I've seen a girl!Jane AU before, but it could be interesting. Might have to be more changes than usual with genderswap AUs, though, because of the clothes if nothing else.

Ooh, or an AU where the wife was the one who wasn't killed by Red John and is now working with the CBI.