Flakvierling

The Flakvierling is an anti-aircraft weapon that fires the 20x128mm cartridge. Based upon the idea of putting four 2 cm Flak 30 guns onto one mount, the Flakvierling was a very successful anti-aircraft gun used throughout WWII by the Germans.

Call of Duty 1 and UO
The Flakvierling appears in Airfield to take out the incoming Stukas that threaten to kill you before you can escape. While somewhat slow at first, it does it's job very well and can take out an enemy plane with one three or so bullets from the gun.

Call of Duty 2
Exactly the same as CoD1 and UO, only it's used in Assault on Matmata. You are ordered to use it at the very end of the mission to take out German Stukas. It doesn't overheat or run out of ammo so you have nothing to worry about besides the Stukas.