My favorite canon DBZ character is Vegeta. No one trains as hard as Vegeta and he's had more character twists in the show than anyone. My favorite non-canon character is Broly. Broly was pure power with no restraints like fear, compassion, or mercy. He also IMO had the potential to become the most powerful character in the series.
My favorite part about DBZ is the DBZ thread already made. 😐
http://www.killermovies.com/forums/309912_123-the-official-dragonball-z-thread#post9055880