I love crossovers. I like the more unusual ones, if they can keep everyone IC and make the universes work. YuYu x Inuyasha and Naruto x Inuyasha are my favorites, but I'm reading a few DBZ X Inu and NCIS x Inu that aren't too bad.
The absolutly most unusual crossover I have seen to date is Full Metal Alchemist x MASH (as in the 70's tv show).
I started reading it, expecting it to be crap and give me a good laugh. The author is making it work, as strange as that sounds, and it is one of the better crossovers I've read.