No contest.
Daffy Duck.
The original MAD version before Chuck Jones got his mits on him.
What about the critters found over at Joe Cartoon ?
I love that poor, poor gerbil–
“Smokin’ eye boobies!”
“Bite. Me.” (points)
Bender
Johnny Bravo
Dexter from Dexter’s Lab
Ren and Stimpy
Are we including CGI charcters here? If so:
The Sabre-Tooth Squirrel from Ice Age
Donkey from Shrek
(And the LEAST Coolest Award would go to Jar Jar Binks…)
Here here, RobuSensei. 
Captain Harlock.
Leela
I can’t believe we had folks that like Daria. Never met one before!
I would like to second Gir, Third Daria, and add Cosmo from fairly odd parents.
And let us not forget Professor Frink or the Warner Brothers (and warner sister).
Shut yo mouf! Or, better stil, go see Cowboy Bebop: The Movie.
I saw it on the big screen. Coolest cityscape animation ever!
Or better still, see the anime Metropolis.
Soundwave, definitely. Completely unflappable, that machine, and–best of all–he carried his buddies around with him in his chest.
I mean, they shot out of his chest, like he was some wacky, techno-driven Greek god giving birth. The voice wasn’t bad, either.
Betty Boop.
She was a nightclub singer, smoked dope and had sex with a dog.
I’m at a loss.
It’s an absolute deadlocked tie between Optimus Prime and Homer Simpson.
– Shawn K.
Stewie from Family Guy, Dr Zoidburg from Futurama (though anything that has or looks like it has come form the sea and is alive and scuttling around scares me more than anything else, but i can bear to watch him because hes only a cartoon.) and finally, and I’m shocked that nobody else has mentioned him (unless i didn’t notice), Spongebob Squarepants.
Spongebob, while zany and fun in a drinking from the nuclear runoff water kind of way, is decidedly uncool.
What criteria are you using?!? 
Bosda Di’Chi of Tricor is very close with Faye but come on dont tell me you discounted Ed seriously shes got a cool ride (Episode: Mushroom Samba, lots of bounty hunters in souped up cars and Ed… on a scooter) and a master of disguise (The Movie: “Hey little boy” “Ed’s not a boy Ed’s a little girl” “get away kid you’ll ruin my reputation”) and her names longer… oh wait im just gonna second a vote for Faye Valentine.
OK, I see your point Cainxinth, but i love the little guy!
either a sootball or the catbus.
Japanese:[ul][li]Shuichi Shindou[/li][li]Kaworu Nagisa[/li][li]Utena Tenjou[/ul][/li]
American:[ul][li]Lisa Simpson[/li][*]Bugs Bunny[/ul]
Daffy Duck
Droopy
Golgo-13
Bugs Bunny
Spongebob Squarepants
For American cartoons I have to say Eric Cartman. Anyone who can trick another person into eating their parents has got to go on the list.
For Japanese Anime I’m going to show off my immaturity and go with Vegeta. He’s a prince, he has a planet named after him, and he can blow up your planet with a wave of his hand.
I am the prince of all Saiyans once again!