I don't know if you've already found some good anime by now, but I guess I'll throw in a few myself ^^

First, NHK ni youkoso/Welcome to the NHK. It is not an action or mecha series though. Rather a psychological/slice of live kind of thing. What I liked about this anime was the more mature approach. It has quite some humor, but no stereotypical anime jokes It tells the story of a college drop-out who NEVER leaves his house (hikkikomori) and who sees conspiracies everywhere.

My second suggestion is Speed Grapher. I've only seen one episode of this, 2 years ago or so ^^;. I remember it being serious, a bit dark and it has action. I think it meets your interests.

I hope you'll like these.