Ear Notch

Bob the Mouse is from the wrong side of the tracks, a true scrapper from the bad side of town but how do you show this easily? Add some notches to his ears for that tried and tested "been through it all" indicator. The ol' 'chunk out of the ear' character design trick has been around for some time and most commonly appears on animated animals. On the Sliding Scale of Anthropomorphism this can apply to almost all points from Nearly Normal Animal to Funny Animal (though can appear on Petting Zoo People) as long as the ears are still large enough and/or discernible as non-human.

It acts as a simple indicator of a character's alignment or temperament if within a group, usually denoting tough or evil traits. It usually is displayed on characters within the rodent species but can also appear on cats and other species with ears large enough to show it off.

Sometimes can be used for added character in a Cute Little Fangs sense where the character isn't at all gritty and/or bad. Tangentially related to Good Scars Evil Scars.

Has nothing to do with the ear of Notch, the creator of Minecraft.

Anime and Manga

 * Boss in Hamtaro.
 * Giro, the villanous wolf leader from Arashi no Yoru Ni, due to him having one of his ears bitten off by Mei's mother before telling her son to run away as he and the other wolf maul her to death.

Comic Books

 * Gen in Usagi Yojimbo has a broken horn.
 * In the comic strip Outland by Berke Breathed, Mortimer Mouse (a parody of Mickey) has a bite taken out of one ear--supposedly the result of a scuffle with Disney exec Michael Eisner.

Film-Animated

 * From The Lion King II, Zira.
 * Within The Lion King trilogy (and non-canon series), Ed the hyena has a few ear notches.
 * In Liloand Stitch, Stitch, as seen in the TV Tropes page image for the series.
 * Buck from Ice Age 3: Dawn of the Dinosaurs.
 * From Oliver and Company, Ignacio Alonzo Julio Federico de Tito.
 * Ronno, the tough deer Bambi has to fight to defend Faline.

Film-Live Action

 * Splinter from Teenage Mutant Ninja Turtles had one from when he was still a regular rat in the live action films. In the computer generated sequel, he doesn't, prompting one of the directors to joke in the commentary that he's had some work done between films.
 * Tsu'tey from Avatar.
 * The mother tiger from Two Brothers.
 * Alvin in the live-action adaptation of Alvinandthe Chipmunks has a notch in his ear, perhaps to identify him as a scrappiest member of the group.

Literature

 * The Dresden Files has Harry's dog Mouse with a notched ear. When Harry first gets the puppy he notes that its probably a sign the pup is either more brave or more stupid than the rest of the litter.

Web Comics

 * In The Intrepid Girlbot the Big Bad Raccoon -- but not Big Bad -- has an ear notch.
 * After, there are a lot more notches to be had amongst the rest of the raccoon population.
 * Kevin and Kell: Subverted a little, Rudy tries to convince Kell to let him get a designer ear notch. Of course, she is less than enthusiastic about the notion.
 * Buwaro in Slightly Damned has ear notches. He's got Cute Little Fangs too, for what that's worth.
 * In the Furry Basketball Association, Buck Hopper, and Cheeto Wolfote both have damaged ears. Bruce Bounder is missing half of one.
 * Lackadaisy: Rocky has a notch on his ear - which he got playing with a gun because he thought it made him look dashing.

Western Animation

 * Rita from Animaniacs.
 * Furrball from Tiny Toon Adventures.
 * Modo from Biker Mice From Mars.
 * Don Karnage from Tale Spin.

Real Life

 * Invoked for livestock as a method of herd identification. Some of the more commonly notched livestock species are pigs, sheep and reindeer.
 * For aquatic creatures it's often the dorsal fin that's notched to assist with individual member identification.
 * Rats and cats can gain injuries through fights which result in ear notching.
 * A notch in the left ear on a cat can also mean a stray has been fixed, which is somewhat less badass.