This is simply the best OVA, and perhaps series ever produced. Basically an alternate telling of Gunbuster, but as a parallel of sorts. The original series, from the 1980's, didn't get too much recognition until Gainax really hit mainstream with Neon Genesis Evangelion. Diebuster, from the director of FLCL, takes a lot from that series as far as animation style, and improves upon it greatly. The six episode OVA has some of the best art and animation and just does an incredible job overall.