As a kid, I HATED Daffy and Donald Duck because they just seemed to be like the villains because of their own greedy agendas. And that in mind, it always seemed to me that Plucky Duck in Tiny Toons should've also popped out of the villains' box in the first episode.
Also from Tiny Toons, Elmyra and Montana Max, naturally.
Pete from Goof Troop, but who didn't?
And thinking back now, I wonder why they kept Roy Rooster around much in the U.S. Acres cartoons on Garfield & Friends because he was always slacking off his work and he was always stealing things, on top of the humorless practical jokes he was always playing.