Throt the Unclean
Throt the Unclean, a skaven special character in Warhammer Fantasy, is the most infamous and madly inventive mutators of Clan Moulder. Originally appearing as little more than a beefier Packmaster with a unique weapon in 4th edition, he became far more unique in subsequent editions.
Throt is a mutant, as least partially due to his own eager willingness to experiment upon himself. This has left him with several distinctive physical traits; he has a third arm on the right side of his body, he has replaced a missing left eye (gouged out in a fight with a long-dead rival) by hammering a chunk of raw warpstone into the socket, and he is grotesquely fat. This is a result of experiments he has done to himself, which have pushed his metabolism to insane heights even beyond those of normal skaven (which should make him grotesquely thin, not fat - go figure). Throt can regenerate like a troll, but he suffers from a ravenous hunger even beyond that of normal skaven - it's actually part of his rules that he has a chance to devour a member of his own unit every turn, even Rat Ogres!
Crazed but incredibly talented, Throt has fathered countless litters of progeny and outlived most of them, and produced many, many different abominations against nature. In White Dwarf #311, it's even stated that he has perfected the art of transplanting minds, including cross-species transplants - much to his dismay, as his first true success in that field was Ghoritch, who has since escaped his control and now holds power almost equivalent to Throt's own. Oh, and due to his capabilities, he can murder everything that is as big as a Rat Ogre and above, making him an insanely effective monster hunter. Did we mention he can do this BY HIMSELF?