I had to watch this, since I just recently bought Halo : Reach.
Good work! Like Warbandit87 said, the camera angles/panning/zoom was what really made the video good.
The story involved was good as well, plenty of humor in the battle, as well as when Mr. Dad acivated and got "locked" in Armor Lock (Haven't done much online play on Reach, but AL is my favorite upgrade (next to camo) in campaign).
A touching end too, the boy grew to what looked to be an adult sized shadow.
One thing that got me though, was that the spartan was still alive in there after many years without nutrition O.o Well, they do say "Spartans never die, they just go MIA." XD
Nice work, and happy animating.