I saw this video a couple of days ago and it is so funny. Basically, the people behind the video (Tobuscus), take game trailers and put a voice-over on top of them. Instead of speaking for the characters of the video, they tend to describe the actions in tone taking place in a literal sense, they also feature other videos but this one definately stands out without competition.
Of course, like any other video of this kind, the fun factor relizes heavily on knowing what Assassin’s Creed is and you must have seen the original trailer, otherwise funny will only mean dull in this case.