 If you liked
Ao no 6-gou
|
 ...then you might like
Armitage III
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Although dealing with completely different subjects, both animes have a nice mix of action and things that make you think about; both are (somehow) sci-fis. And: they are on a similair graphical level (although Blue Submarine No. 6 sometimes uses CGI in a not too skilled way).
By the way: both animes exist as single movies and 4-part OVAs.