Armored Troopers Votoms is a great show. The main character starts off as an elite soldier who deserted the military, down on his luck and searching for the military officers that forced him on a special mission and then attempted to kill once once he witnessed too much. The show deals with transhumanism on a small level as the main character develops from a cold-feeling, silent but strong sort of loner into someone who experiences love, friendship and becomes much more than a mere human being, literally.
The show starts slowly and the main character initially comes off as a naive person, but the show picks up once they leave the initial setting of the city for the (Vietnam War-like) jungle story arc, where there is a lot more action because they were done with introducing the main character and his supporting friends. The action will appeal to you if you are interested in small, high mobility mecha. The majority of the action takes place on land on the various planets that make up the galactic setting of the series, but there are a few episodes that feature zero gravity combat.
Edit: Oh, and if you don't like Votoms' story, try Armor Hunter Merowlink. Same universe/setting, except it's about another guy seeking revenge on his commanders for having his war buddies killed in a suicide mission, defending against a large advancing enemy force. His squad has their regular equipment taken away and are issued obsolete anti-armor rifles instead.
Merowlink is the only member of his squad to survive, and is then framed for an unrelated scandal where his commanders stole a large amount of precious resources. The badass main character can no longer tolerate this bullshit, so he breaks out of confinement and hunts down his former superiors involved in the scandal by killing them all with the same anti-armor rifle he was forced to use in the suicide mission. He takes on enemy mecha on foot, often employing clever traps and tactics to make up for a any weaknesses. A cool thing about the story is that each episode features different terrain, and shows how the main character uses the terrain to his advantage. For example, the first episode is desert, others are jungle, forest, arena.. etc.
