I know there is already a threat about a similar topic. But that´s just about Skyrim. There are many games where you can do epic battles. :P

My best fight so far was a fight against 10 tanks on the highest difficulty in L4D2. I was playing alone (also without bots) and didn´t use fire. I started pretty easy and took it to another level every time. I think 10 tanks on expert is near the limit as long you can´t do perfect bunnyhops while avoiding becoming killed but also kill the tanks at the same time. Everytime when I reloaded my ammo was refilled because I really needed a lot of ammo.

https://www.youtube.com/watch?v=sDFMu2YKL5Q