a)cat
dog (assuming hes not a crazy german sheperd or otherwise large, angry, starving and agressive)
b)cat
dog (any dog)
horse
wolf
c)
cat
dog
horse
wolf
elephant (are revolvers able to pierce an elephants skull? if not, count this one out)
(I left out lions, bears and tigers because they tend to be fairly quick, so even with 3 bullets, I might only get 1 shot)


The heirarchy is really messed up though, since size does not equal danger always.