Mister Descriptor

"Damien: What is your name? Elliot: Um, well, what with me being a cat and all... Cat? Damien: All of you animal people have horrible names. Elliot: Well, uh, what can you expect? We were named by scientists, not writers or cartoonists."

- El Goonish Shive

Characters with only a surname, which describes them.

Sister Trope of Something Person.

If the word for their surname doesn't have any obvious relation to the character in question, it's Mister Strangenoun. If it's not a character but an offhand description of a prop, look toward I Call It Vera (or the demonstrative I Call Him "Mister Happy"). If their name reflects their color, it's also Colorful Theme Naming.

Comic Books

 * Mr. Men
 * The Riddler of Batman, born Edward Nashton, legally changed his surname - making him E. Nigma.
 * Mr. Sinister of X Men fame, who took that name because it was the last word his wife said to him as she died, when she realized what a monster he was.

Film

 * Ditto Reservoir Dogs.
 * Mr. Furious in Mystery Men.
 * Mr. Glass from Unbreakable.

Live Action Televsion

 * Mr. Big in the first episode of Get Smart.

Literature

 * Mr. Pump in the Discworld novel Going Postal. Of course, he's a Golem who was employed pumping water at the bottom of a well for a few hundred years, so it's an apt description (his 'name' was previously Pump 19)

Radio

 * Mr. Show with Bob and David

Tabletop Games

 * The characters in Clue are named after the color of their pieces: Mr. Green, Mrs. White, Ms. Scarlet, Mrs. Peacock, Colonel Mustard, and Professor Plum.

Theatre

 * The song "Mister Cellophane" from Chicago.

Web Comic
"Damien: All of you animal people have horrible names. Elliot: Well, uh, what can you expect? We were named by scientists, not writers or cartoonists."
 * El Goonish Shive chimerae are usually called by some reference to their "beast" part (like Nioi/Kaoli with a Bilingual Bonus). So despite Elliot being horrible at lying his captor mistaking him for one of these didn't even doubt:

Web Original

 * Invoked with the Mister Collector series from the SCP Foundation. They were built to be that way.

Western Animation

 * From South Park, Mr. Garrison's puppet Mr. Hat, followed by his replacements, Mr. Stick and Mr. Slave.