Shredder rotors
I'm impressed by metal shredders. A large funnel into which you chuck metal scrap and at the bottom there are two slowly contra-rotating cylinders with sparse teeth. Just about anything goes in (old cars etc.) and metal shreds come out.
How about a wedge-shaped open-mouthed robot that did nothing but get close to any type of opponent and try to suck it into the mincer.
Biting the hand that feeds IT
