Jak 3

Story related and cannot be missed.
Just after you enter Port City, you will be given a mission to destroy incoming Blast Bots. You will have to destroy them before they reach the house that you start at. I suggest using your Vulcan Fury or Arc Wielder guns, ammo for them will be plentiful, and they are effective at dealing a lot of damage to a single source. You will have to go to the side that shows two Blast Bots on the map, destroy the first one, then head back to the other side, destroy the lone one, then destroy the last. That way they won’t get close enough to your base of operations to concern you too much.