Jak 3

Story related and cannot be missed.
You will be sent to defend Port from the invaders. You will be put in an overhead view, and will just be defeating all the enemies. You will have unlimited ammo with the base gun, and guns will appear as you go that you can pick up for limited ammo with them. The only difficult part of this is the third wave in which you have to protect some townsfolk. Only one of them has to survive, but they die fairly easily, so be quick about killing the enemies. Once you have defended all the areas, you will receive this trophy.