Unlockable: Level 4 Weapons
Raise a weapon type to maximum, and then get 500 kills.


Hint: Level 4 Weapons

When trying to get your level four weapon, which requires you kill 500 enemies, try the following. Press the directional button down so your allies don’t kill everybody, and leave one or two people per base alive. When waiting for reinforcements to arrive, find enemy officers, kill the foot soldiers accompanying him first, then finish him. Do this for every officer as many times as they come back. When you’re around 420 kills, you can then take all of the bases and get the kills needed, including the main base. If you fight in the main base before getting at least 420 kills, the probability of you reaching 500 kills is minimal.