Not greatest overal, but dennis rodman had to be the greated nutcase of all time. He could skip a weak of practice, party every night and run off to vegas between games. But he'd still come in, grab 16 rebounds per night and totally destroy anyone he was defending. I still remember watching him play against malone in the finals. He totally destroyed him, whenever kukoc was guarding malone he'd play like karl malone, but when rodman guarded him he played like post lockout shawn kemp.
Not only did he shut people down he got into their heads. And unlike artest (who isn't his equal defensively anyway, but also screws with people) he was an act. He'd bring you to the point of wanting to punch him and then just let you go off, while he just sat back and watched.
Though this is when he was on chicago (he was good, but not really crazy, for detroit). He was a great addition to already great teams who didn't really "need" him, but was destructive on average or below ones. You had to be able not to care about him outside of games, cause if you depend on him to do team things or be involved in practice then you were going to have problem.