My favorite character/show's signature exclamation is:

Pinky and the Brain
• Narf!
• Zort!
• Troz!
• Poit!
• Egad!
• Fjord!

Simpsons
• Doh!
• woohoo!
• cowabunga!

Batman and Robin
• Pow!
• Zap!
• Holy $x!

Superman
• Great Scott!
• Great Ceaser's Ghost!

Little Rascals
• Otay!