No one has mentioned Tengen Toppa Gurren Lagann yet, so I'll throw that out there. It's a hot blooded, manly mecha epic that starts out literally in Plato's Cave (being Gainax and all) before expanding to a science-fiction setting. It was the kind of show where every episode I would think "that is the most ridiculously awesome thing I have ever seen", only to have it topped by the next episode.
I'll second the recommendation for the original Dirty Pair (series + OVAs), which aren't exactly deep sci-fi, but were a lot of fun. Outlaw Star was cool too, but you've probably seen that already on [adult swim]. Gunbuster (Top o Nerae) uses the old "fighting space monsters with mecha" plot, but stays mostly in the realm of hard science with educational chibi bonus segments, and packs a heartbreaking plot into six short episodes.
And in the "something completely different" category, I'm going to recommend a couple just because: Azumanga Daioh (cute girls enjoying high school) and Revolutionary Girl Utena (elite high school, secret plots, roses, sword fights, fairy tales, deconstruction, roses, shadow girls, and more roses).
-- ∇×V
I'll second the recommendation for the original Dirty Pair (series + OVAs), which aren't exactly deep sci-fi, but were a lot of fun. Outlaw Star was cool too, but you've probably seen that already on [adult swim]. Gunbuster (Top o Nerae) uses the old "fighting space monsters with mecha" plot, but stays mostly in the realm of hard science with educational chibi bonus segments, and packs a heartbreaking plot into six short episodes.
And in the "something completely different" category, I'm going to recommend a couple just because: Azumanga Daioh (cute girls enjoying high school) and Revolutionary Girl Utena (elite high school, secret plots, roses, sword fights, fairy tales, deconstruction, roses, shadow girls, and more roses).
-- ∇×V