A group called "Your-Mom" fansubs took some liberties with their Code Geass translation.This was later admitted to have been an error in attempting to determine how "rude" the choice of phrasing originally was. An unusual example from an official release - Disney's dub of Princess Mononoke took a harmless line ("This soup tastes like water!") and punched it up ("This soup tastes like donkey piss!").
Too bad they release series when they feel like it and incur some Narm when leaving some perfectly translatable words untranslated. Fortunately, other than that and translating Lolicon as a word that means "Child Molester", their translations are alright. Emphasis on very.) They especially are fond of using the word "joder" (Spanish for "fuck"), which they seem to find a way to work into just about every circumstance, even if the Japanese word is something like the rather mild "shimatta", or isn't even swearing (Like "Impossible!" or "This is bad!"). Spanish fansub AnimeUnderground seems to work by the following rule: "If there's the chance of using slang/ swearwords instead of a normal word, then do so, no matter the context or who's saying it.Shinsengumi Fansubs added quite a bit of cursing to its fansubs of Flame of Recca and Rurouni Kenshin.This also happens in some manga scanlations.
There's at least one Bleach fansub out there that gives Nnoitra constant F-Bombs.This sort of translation even gained the nickname "fifteening", for the age rating that resulted. Manga Entertainment, particularly their UK branch, was notorious for this as well in their earlier days.
The Anime Labs translations in particular were infamous for this, such as Vegeta yelling at Android 20 to "Come on out, you coward! Show yourself!" getting turned into "Come out, you candy-ass faggot!" In comparison, official translations of the franchise never use profanity any more extreme than "bitch".