The Martian Manhunter began existence as a sort of ex machina kind of hero, using his advanced Martain technology to accomplish pretty much whatever he needed. His powers included superhuman strength, damage resistance, flight, regeneration, intangibility, invisibility, telepathy, telekinesis, and generally whatever else he wanted. However, he was vulnerable to, and terrified of, fire, so any halfway educated caveman stood a chance against him.
Despite being a founding member of the Justice League of America, he only reappeared sporadically throughout the silver age, usually as a storytelling foil. It wasn’t until the character was dredged up in the 80’s that he was given a cohesive backstory. Most of the time the Manhunter is the same guy, J’onn J’onzz, or “John Jones”, but in some future story arcs he is replaced when Miss Martian takes on the title.
Since the silver age he has been a mainstay of DC’s comic lineup. While in no way a household name, television exposure and a super catchy name have made him at least recognizable.
References: [wikipedia.org: Martian Manhunter]
Metahuman Database 