Revolvers Are for Amateurs

If a character who has little combat experience needs to kill someone or defend himself, chances are he's going to be packing a revolver, especially a snubnose revolver, instead of a semiautomatic. The less advanced design, smaller ammo capacity, and the shorter barrel are a good visual metaphor for the character's vulnerability and inexperience in combat.

One reason for this is that revolvers are simple and reliable firearms compared with more modern designs. There's a minimum of moving parts compared to a semi-automatic, they are less picky about what ammunition they'll take, and they don't jam under normal circumstances, so they're lower maintenance and more reliable for someone who doesn't have a lot of experience with firearms in general. Revolvers being cheaper, and therefore something you're more likely to find on an amateur rather then a professional who has more money invested in his firearms is also a contributing factor.

Doesn't count for characters who live in a time where semiautomatic handguns were rare, unreliable, or nonexistent. Doesn't count for characters experienced in gunfighting who use small revolvers as backups to other, larger weapons or for easy concealment. Also doesn't count for modern characters who are Western freaks.

Compare and/or contrast Revolvers Are Just Better, where someone who does know what they're doing decides to pack a wheelgun.

Anime and Manga

 * Zig Zagged in Ghost in the Shell. In Stand Alone Complex, Togusa is frequently criticised for carrying a revolver. In the Ghost In The Shell manga he's convinced to carry a semi-automatic, in the third movie (the one based on the Anime series) he's finally . It's implied that he thinks Revolvers Are Just Better or is simply old fashioned (old fashioned family values, uses a gun almost as old as he is, few cybernetic implants).
 * It also allows him, in both the first movie and an episode of the series, to fire some sort of tracking device onto a car.

Film

 * David Della Rocco in Boondock Saints is given a "six shooter" when his mafia bosses set him up to be killed--unbeknownst to Rocco, he was being sent to kill nine guys instead of the two guys they told him he would have to kill. He later uses the gun in his first vigilante murder.
 * Ray Ferrier in War of the Worlds brings one with him when fleeing from the alien invasion.
 * Seen in Reservoir Dogs where Mr. Orange and Mr. White try to carjack a woman. The woman hastily pulls a snubnose revolver and manages to shoot Mr. Orange.

Live Action TV

 * Noah Bennet in Heroes uses a snubnose revolver the first time he tries to kill a person with special abilities.
 * Perseus, a computer programmer, defends himself with a snubnose revolver in NBC's Chuck.

Video Games

 * Probably why Alan Wake, a thriller writer with supposedly limited experience with firearms, primarily uses a revolver.
 * Invoked in the first The Godfather: You are a newcomer to the mob and the first gun you get from your mentor is a snubnose. You only get better weapons later.

Real Life

 * This is absolutely Truth in Television. Revolvers are recommended for beginning shooters or people just looking for a weapon for home defense, due to their relative low maintanence, ease of use, and high reliability.