Diebuster, known in Japan as Aim for the Top 2! (トップをねらえ 2!, Toppu o Nerae Tsū!?) is a six episode anime Original Video Animation (OVA) series created by Gainax in 2004.

The first episode was aired on October 3, 2004, while the final episode was released on August 14, 2006. A movie, officially titled Top o Nerae 2! & Top o Nerae! Gattai Gekijouban, retells and recaps the end of the first Gunbuster OVA and the finale of Diebuster. It was scheduled to air on October 1, 2006 at the Tokyo Anime Center's 3D Akiba theatre.

Also called Gunbuster 2, it is the direct sequel to Gunbuster, but is animated in a 16:9 widescreen aspect ratio, rather than the 4:3 aspect ratio used in the majority of Gunbuster. It has been licensed for American release by Bandai Visual USA as Gunbuster 2. Additionally a manga adaptation of the series is available in Japan.

Source: Wikipedia