HAN-S is a massage-bot aboard the Axiom. The reject HAN-S suffers a disfunction that causes his arms to flail about. Thus, it is difficult for him to control his arms when they thrash about. It is possible HAN-S suffers from repressed anger. Following the destruction of the steward bots (after which he stands over them like a champion boxer), he seems to have better control of his arms.
HAN-S also appears in the video game where he destroys cubes and crates blocking WALL-E's path.