Word Buster is a filter for Garry's Mod, it censors "bad words" with the character of your choice. It uses the List-of-Dirty-Naughty-Obscene-and-Otherwise-Bad-Words (License) which contains more than 350 english words and then converts them into patterns so that it can catch most variants of the banned words.
Simply drop word-buster into your addons folder and customize lua/sv_config.lua to your needs. To add or remove words simply edit the language files in the data/wordbuster folder but remember that the censor character cannot be present in any of the loaded language files.
Hey! It's open source feel free to upgrade it and add words to the list. coughcough Pull Requests coughcough