[quote=@edgeout]
I want a bot that can have superior melee skill, with [u]quickness[/u] of an assassin
[/quote]

Well as [@Zero Hex] before me mentioned Belzelga would be one thing in melee 
[hider=Ramble about Belzelga melee and speed]
(though it'd really be bland as either it'd be something like OHK or or just a punch more in line with rest of the bots but it really would not be fast either way and could be outmaneuvered and for plot's sake most fights would have to be like that)
[/hider]and as mentioned in above ramble it would still slow.

as also pointed out by [@Zero Hex] (should we give him some more recognition?) [url=http://medarot.meowcorp.us/wiki/Nin-Ninja]Nin-Ninja[/url] would be close(st) to your description of a bot and I'll be happy to do that but be sure to say if anything else caught your eye.