It is Max's basic weapon. He has one with unlimited ammo, but others with limited. Just regular pistol.
UZI
Automatic, not very powerful, but fast weapon. You can find it on every level - it's common weapon.
Shotgun
It is very powerful weapon. But it has two disadvantages - it is non-automatic, and shoots very slowly. But it's still very useful weapon.
Gatling Gun
The best of Max's weapons in MDK 2. It's extremely fast and powerful weapon. Just grab it, and kill everyone!
Raygun
It is some kind of plasma gun. Not very fast, but it's powerful. Raygun shoots with red balls. It's useful, but can be found only in further levels.
Guided Rockets
Very, very powerful, but there isn't a lot of ammo in it. Besides, it can be found only in few places, and shoots slowly. But rockets are very powerful, and makes big damage. If you find it, try to keep it for a tough spots.