This video clip of an animated version of the Garth Ennis and Amanda Conner comic The Pro - a comic I just recently learned about and bought - is really, really not safe for work, and, depending on your perspective, is probably also NSFL (Not Safe For Life).
However, like the comic it's based on, it's really funny.
(Note for Scott: It was done by the same company that does Metalocalypse)
Among the NSFW/L elements:
Really, really naughty language (consider that it was written by someone from the UK, where words that are a little more taboo here get flung about rather freely)
A depiction of oral sex
Extreme acts of violence
More oral sex
Did I mention the language?
Embedding is disabled, but you can, if you so choose, watch it here.