Does the animal need to be mammalian? Could it be reptilian?
Most mammals die when shot with relatively low power (civilian) weapons. Rabbits die instantly from shock when shot with a .22 (I nicked a rabbit's ear with a .22 long once, and it died from shock), a fox can take at maximum two .303 rounds, although the first one is extremely likely to kill it outright or cause a mortal wound. Kangaroos I've seen take up to five .303 rounds. Pigs are resistant little buggers with all that fat slowing down bullets quite a bit before it can really do much damage, however pigging dogs are specifically bred to bring them down. I can't say too much about elephants and rhinos or hippos because I live in Australia and haven't been on any (legal or otherwise) safari hunts (Although in Borneo(?) there was the incident with the SASR where a patrol ran into the bad side of a rogue elephant causing the first SASR death on active duty. The elephant was shot with over eighteen SLR rounds, twenty-four Armalite rounds and the elephant went on to wreck someone else's day after goring one of the patrol).
However, the same is pretty much true for humans, although we have the benefit of being able to kill the other guy with the same kind of weapon he's using. Hence the military
Reptiles have the benefit of natural armor, while not on-par with manufactured human body armor, I've seen two crocs duke it out to each other and their scales save them from many injuries, something that rarely happens to mammals (not counting rhinos, elephants, hippos, maybe even wild pigs who have a lot of fat).
Anyway, reptiles Y/N?