9th and 10th US Cavalry Regiments - AKA, along with the 24th and 25th US Infantry Regiments, as the Buffalo Soldiers. They were some of the finest, and toughest, soldiers to ever serve in the US Army.
442nd Regimental Combat Team (442nd Infantry, 100th Infantry Battalion, 522nd Field Artillery Battalion, 232nd Engineer Company, 206th Army Band) - tough guys who overcame the disgusting and illegal behavior of the US Government during WWII to forge a combat record second to none - GO FOR BROKE!
1st Battalion 333rd Field Artillery - my first TO&E unit.
11th Armored Cavalry Regiment - especially when they were stationed along the border with East Germany - Death Rides A Black Horse.
40th Infantry Detachment (ROC), my current unit.