Texhnolyze, Gungrave Recommendations
They both have a similar feel to them. Although Gungrave has more of a depressing feel. But both them are about to low poor people guys whom ended up becoming higher up bosses in Gangs. Both becoming the bosses most trusted people. Both no longer fully human use it to there advantage to keep what they treasure the most alive.
Gungrave and Texhnolyze have quite a lot in common. Brandon Heat and Ichise are very similar characters. They end up loyally serving an organization with their prodigious fighting abilities, they're both withdrawn and not very talkative characters. Some of the concepts in both series are similar, and although the style is a bit different, Texhnolyze being a bit more grungy, I'd say they both have a similar feeling to them. If you like Texhnolyze you'll probably like Gungrave, and vice versa.
Texhnolyze is a similarly grim and depressing show that tackles many of the same themes Gungrave does such as violence and the will to power. It's also divided into two distinct halves with a different flow, much like Gungrave.
Both have main characters who are no longer human. Despite this, they fight to protect people they care for.
They also belong to a gang, and work their way up the ladder, remaining loyal to their leader.
The technology used in their transformation is also used to create a revolutionary army, of sorts.
The main characters are rather similar. Both Brandon and Ichise end up physically modified, but that is less important than their ambivalent, confused outlook on life. Both join an organization they initially dislike and then try to establish their identity in relation to it, with nearly identical results. The tone/feeling of both series is quite similar as well. Bonus similarity: Both feature instrumental intro music.