In order of preference:
1) Celtics. I'd probably be a Boston fan if the Jazz ceased to exist.
2) 76ers. Biggest underdog at this point.
3) Pacers. Meh.
4) Spurs. I don't like 'em but I'm used to them winning.
5) OKC. Oklahoma City hasn't had a team long enough to deserve a title. ) Also Fisher is a tool. Impressive fanbase though.
The Heat can suck it.