For robots, you clearly just put thunder on the whip.
Irvine using shotguns when he is a sniper is dumb, but the weapons are fine and it makes way more sense to use a shotgun in close combat than a sniper rifle. In his defence, he uses a proper sniper rifle when he's actually being a sniper who breaks down under pressure.

In either case, harpoon is the dumbest weapon, closely followed by the discos thrower.