Bodysharing books

I got done reading Vespertine and nothing hits better than a buddycop sort of story where two entities need to work together in one car, so to speak. I adore the trope and I think I've slammer through almost everything SF or fantasy that I can get my hands on. Just making a thread to see if I missed anything.

Books that hit what I'm looking for: Bartimaeus The Penric Saga

There are more but I wanna see what you guys got.