SSBB, You can kill rodents, foxes, wolves, penguins, hedgehogs, falcons, frogs, turtles, crabs, dragons and even people(Yes that includes women and children). Most of the time that's even the main objective. You can even use blunt weapons like baseball bats and hammers to smash the children in the head to kill them.
It's a very cruel game.

In Oblivion, you can fight random dogs, wolfs, horses, deer, bears, crabs, etc...

Mario mercilessly stomps on the heads of innocent turtles, and then uses their shells as weapons.

nearly every game that dosent revolve around a sport or mini game colelction

http://www.youtube.com/watch?v=E9uMBx1Zqgw look at the video my brothers made, its kinda fun, I dont care since its a videogame and not real life, they actually like animals

Oh, the game in the video is GUN for the ps2

I really enjoyed shooting cats with my sniper rifle in Deus Ex

Fable series: Chicken Chaser!

cow tipping in fallout 3

Mario rides on Yoshi, and he can even jump off him to safety while Yoshi falls to his doom...