I dunno if I would call it my favorite word, but I've enjoyed using 'nimrod' recently. It's fun to say and the current meaning has an amusing etymology. Nimrod was a biblical figure whose name originally meant something like "skilled hunter." It came into modern use with the meaning of "incompetent person" thanks to a cartoon. Bugs Bunny called Elmer Fudd Nimrod after he fucked something up when hunting, basically the same as calling someone Einstein after they say or do something stupid, and the sarcastic meaning stuck.
I really enjoy words with odd etymologies. I'm a nerd.