506th parachute infantry regiment (us army)
One of three parachute regiments that made up the 101st Airborne during World War II, the 506th saw combat service from the D-Day invasion to the end of the war in Europe, and continues as part of the 101st Airmobile Division today. The regiment was made famous thanks in part to the television series Band of Brothers, which focused on the regiment's E Company ("Easy") during WW2.
Depictions of the regiment will almost invariably be of its appearance in World War II, with the "Screaming Eagle" patch of the 101st Airborne worn on the left shoulder. The major visual indicator of the 506th is the "spade" insignia (from a deck of cards) on the helmet, which was done before the Normandy landings to allow for easy identification. (The division's other regiments - two parachute and glider - used the other three card suits on theirs.)