88mm Anti-Aircraft Gun
The German 88mm Flugabwehrkanone (Flak) anti-aircraft gun went into production in 1932 and was first used in combat in 1936 during the Spanish Civil War.
Although originally designed as an anti-aircraft weapon, the 88 would go on to serve effectively against armor and infantry as well. One of the most feared weapons on the battlefields of World War II, it was usually referred to simply as an "88."
Notes
Captain Miller makes references to towed 88's when reporting his unit's actions to his commanding officer on D-Day+3. The 88's had destroyed four Sherman tanks and a few deuce-and-a-half trucks.
A scene that was cut from the film shows Miller's squad, travelling by jeep just after their departure from Omaha Beach, being shelled by 88mm guns. It is at this point that they lose the jeep and a lot of their ammunition. This explains why the jeep disappears, and a somewhat cryptic line of dialog that remains in the final film and mentions the loss of the ammo.