So because I'm a huge anime nerd (and after being inspired by Putnam's fantastic DBZ Mod) I've set about creating several mods based on various anime. Most of these are just beings/creatures added to the raws, but I'm also planning at least one total conversion mod.
The first thing I made was an Elfen Lied mod that gives dwarves/humans an extremely rare Diclonius caste with extra body parts (vectors - made of slade!) that can tear enemies apart. And a random chance to give themselves a syndrome making them CRAZED

After testing in the arena, I find that they can wipe the floor with groups of up to four unarmed humans without injury (though groups larger than 6 do result in the Diclonius getting injured - and a large enough group will eventually kill them). I'm trying to think of how to make them more lethal while still keeping them faithful to the source material (e.g. no super strength or cotton candy skin or anything like that).
Edit: Ok so after tripling the number of vectors, and adding [ATTACK_VELOCITY_MODIFIER:10000], [ATTACK_PENETRATION_PERC:10000] and [ATTACK_FLAG_INDEPENDENT_MULTIATTACK] to the vector attack, my Diclonius has become far more deadly in combat, able to reduce crowds to minced meat in moments. Unfortunately she's still vulnerable in melee - in one arena test run a human killed her with a lucky punch to the upper body. The main issue is she has to be right next to her target to use her vectors (whereas in the anime/manga the vectors were long enough to kill from a certain distance). Oh well...