Someone brought a cat in to our clinic that had brought down a bluejay. It was a big cat (eighteen pounds, with claws like big fish-hooks on all four feet) but we were pretty impressed that any cat could haul in a bluejay and not sustain some damage.

We've also had several (unrelated) cats come in who had shredded full-grown rabbits, and one that killed its owner's sister's Chihuahua. I can't really blame it for doing in the Chihuahua, but those little dogs can be pretty mean.