I like UBB, actually. Eminently hackable, whereas I get lost in PHP code. Also, although it's very touchy about being messed about with, it doesn't have a lot of the problems that phpbb has.. like for example the fact that you can't use quotation marks within tags in just about any field. It also doesn't have some features that phpbb has.

Personally, my favorite board of the moment is vB.. but since I don't have the money for it, and don't feel a strong urge to pirate it, I'll make do with phpbb.