Spoilers Galore...Beware After all this whole site is a Spoiler...Muah ha ha ha..
Oh yes thats his full name. The evil twin brother of Vash the Stampede (who seems to be everyones fave character...grrr.) Ahhhh but Evil is Gooood. There is a little Evil in everyone. Anyway Knives is the "Leader" of the Gung Ho Guns. He is the Mastermind of them....He controls them and uses them for his own purposes. His right hand man is Legato. Knives and Legato both have Psycic powers and are able to control people with their minds. Some say Knives taught Legato how to do this But I think Legato already knew how.
Legato practically worships Knives...who wouldn't. And is willing to do ANYTHING Knives wants him to. Knives is the Counterpart (Sorry Tiara I had to use that word...) to Vash. Vash loves everyone and doesn't belive in killing and will do everything to prevent such actions. On the other hand Knives Hates all Humans (This is a result of the beatings he and Vash got as children on sEEds) And sees no shame in killing. The strangest part is even though Legato is human he still serves Knives knowing his plans. In fact Legato agrees with Knives and sees no purpose in his own life.
Bu if you look at it from Knives point of veiw it would be differant. Knives only wants Vash to join him in destroying all humans and make a garden for them both. Yes it's weird But I Love Knives anyway.