Just killing in the last stage of the game. Bad quality due to bad compression and minimization (when unedited, the vid was 1 Gig). Altair's line is pure irony in this case.
Killing people in Assassin's Creed - using the 'gentle push' action. Guess the game considers it as a sort of suicide. Doesn't alert the guards, either.
An assassin giving himself a blow. Ubisoft tends to chug out the sickest glitches in their games. Click "Watch in High Quality" if you can't really see much of the, err, action.