I've been a huge fan of J'onn J'onzz a.k.a. The Martian Manhunter for decades. I especially enjoyed his 1990's comic book series scripted by John Ostrander and drawn by Tom Mandrake and I still hope for a trade paperback release of its 36 issue run. I'm excited to learn that the new Justice League of America comic series that debuts in March will feature J'onn in a major role. I'll have to check it out!
Check out this great blog dedicated to the character for tons of info.