This is Bananattack.

Maximum Yak Maniac is a multiplayer game, where you and one friend (or you as both people) play as steroid-addicted yaks. The yaks have roid-rage issues, and start to eat buildings and balloons to get more steroids. If the yaks don’t have enough steroids in them, they die, so you need to keep eating needles to give yourself more time. The player who causes the most destruction before dying wins!

An entry made in a 24 hour game making duel against my housemate. The title is from the Video Game Name Generator.

Remarks: Surprisingly good for being made in under 24 hours!
Genre: multiplayer arcade
Credits: Overkill (code, art, game mechanics), mad (music)