Hmm... for the VtM universe as a whole I'd say that my favourite clan is definitely Tzimisce. They don't hide what they are, and their appearances most likely reflect their personalities. (not to mention that their clan emblem is a dragon
In Bloodlines though, my favourite clan must be Malkavian.
They're also geniuses - although the Malk's insanity probably leads to them being underestimated by most. Not to mention spewing crazy lines like 'may I mine your grey matter?' and the fact that there are only two or three characters in the game who understand what you're seeing/talking about was fun.
Lets not forget dementation - especially the part when you trick Samantha into believing that you're her pet turtle, Shelly! :laugh: And then there is that striped hat for the male's final outfit, epic win.
Lol, both my favourite clans happen to be the crazier ones.