HALO: Legends, which is an Animatrix-style take on the Halo Universe.
Now, I'm pretty much a n00b to Halo universe, so the first two features on the disc pretty much helped to lay it out for me.
Oddly enough, though, I have all the Halo soundtracks, (6 total as of now) and have seen trailers, and I don't play ANY games (just NO time or real interest, after being on a computer 12 hours a day).
The music is amazing, among the best soundtrack music I have heard for anything.
The quality of the various HALO: Legends videos varies, but they're all Anime style, along with some full-on CGI....just like the Animatrix.... so I guess your tolerance and love/hate of anime largely factors into this. I've read that some HALO fans are screaming bloody murder though, but that would be par for the course on something like this.

I've got to get out and find me some Black Dynamite tonight.