Flares

A flare, also sometimes called a fusee, is a type of pyrotechnic that produces a brilliant light or intense heat without an explosion. Flares typically give off a red illuminate and sometimes smoke which are used for signalling, illumination, or defensive countermeasures in both civilian and military applications as well as emergency situations.

TV Series
In The Walking Dead (TV Series) season 2 episode, Bloodletting, Shane is seen with Otis at the FEMA Unnamed High School medical center both using flares from a police car to distract the walkers as they went to get supplies from the medical trailer. It worked momentary until the flares burned out and the noises from the flare subsided leaving the attention to Shane and Otis and the sounds of metal canisters and medical supplies clanging in their backpacks.

Comic
Flares are also used in the comic as a means to get the attention of certain people.

Trivia

 * Walkers are temporary distracted by flares as they provide bright light and make a "hissing" noise, once the flare goes out, they go back to "wandering"