The Jack Robot is a staple in the Tekken Franchise.
Prototype Jack is my personal favorite.
He beat Jack-1 in the first King of the Iron Fist.

Both Jack-2 and P.Jack were destroyed in the second one.

http://www.youtube.com/watch?v=O1IpfrkQcU4

http://www.youtube.com/watch?v=ApQlX8qNJDM

GunJack from Tekken 3
YouTube video

The infamous assault with tons of Jack-4s attackign Heihachi Mishima and Kazuya, showing the level of firepower they have.

YouTube video