The black reaper known as Hei from Darker then Black ( those who actually knows his name).
I always love Hei and I always love the way he fights. Being a Contractor he has a special ability and a star ( which is molecular/ electricity manipulation and BK-201 as his star). He also good in hand to hand combat and have amazing speed. Not to metion on the end of his kinfe there is a wire with a carabiner attached to it. Which helps him in every battle he goes into.
That's day 10 next is favorite mech anime.