Flagpole in the face!
Will Christiansen is a professional animator who worked on Halo 4, specifically focusing on the Assassination animations based on his show reel. Halo 4 on a whole is an amazing technical feat, so I love this more individualized look at the game. The animations look great as it is when you're playing, but you really can't but help to appreciate it even more so when we get a focused look.
Will also has a demo reel of his work from Halo: Reach, and seeing the two side-by-side shows you how much Will's work has improved in just a few years.