Giant Alligator (Resident Evil 2)

A normal alligator that has grown to enormous size, big enough to swallow you whole. Most likely a pet of a resident of Raccoon City, who flushed it down the toilet. Now in the virus infected passages of the Sewers, it got infected, and emerged as this monster.

There are two ways of killing this creature, either go in with guns blazing, filling it full of everything you've got, until you're backed up against the wall. Eventually you will scare it away, until Scenario B where you have to fight it again. Using the same tactic in the second scenario will kill it. Alternatively, about halfway along the corridor there's a switch on the wall to release a high-pressure gas canister. If you release it when the alligator is chasing you, it will eventually end up in its mouth. Fire a shot from any weapon to blow its head clean off.