Here's my list.
Daffy Duck (Looney Tunes)- Whether its wise-cracking Daffy or angry Daffy or butt of joke Daffy, he always makes me laugh and there has not been a single Daffy Duck cartoon where I have not laughed.
Bugs Bunny (Looney Tunes)-Always gets the better of his enemy(except on a few occasions). Bugs is the definition of a great cartoon character.
Monkey D. Luffy (One Piece)- Luffy never gives up, always comes through, and defeats his opponents in the cruelest way possible (letting them live knowing that they failed in their scheme). Luffy is a great protagonist, even more so than Goku.
Donald Duck (Donald Duck)-Don't make him mad, he'll become insanely funny!
Lisa Simpson (the Simpsons)- A great character with the most personality in the Simpsons.
The Joker (Batman)- In any incarnation, this guy is mad! And that's what makes him great.
Sgt. Major Kululu (Sgt. Frog)- Sadistic. Insane. Crazy! He makes Sgt. Frog really funny, and without him the show would not be nearly as good.
Stewie Griffin (Family Guy)- His personality seemingly changes every episode, but that diverse rabge of character keeps him fresh and likeable.
Kurama (Yu Yu Hakusho)- The most badass character on the show.
Don Patch (Bobobo-Bo Bo-Bobo) He's not the main character, but that does not make him any less insane and awsome as the others.
If you change your mind about having only ten, here are the rest that I would nominate.
Gohan (DBZ)
Piccolo (DBZ)
Flapjack
Chowder
Mojo Jojo
Eric Cartman
Dororo (SGT. Frog)
Bloo (Fosters)
Dale Gribble (KOTH)
Butters (South Park)