Taurus Bulba in "Darkwing Duck" was severly underused for such a significant villain (If it weren't for Bulba, Darkwing would never have met Gosalyn or Launchpad, plus, Darkwing defeating Bulba was pretty much his big break as a crimefighter). Of course, one of the reasons they didn't use the guy much could be that he always seemed much more dangerous and serious then all the other "Darkwing" villains, so maybe they didn't want to cheapen the character.
Still, I would have loved to see more of him.