I can't beat Manchu Warrior's story, but here's mine:
Back in the early 90's I was in a reserve signal unit at Fort Stewart, GA. At the time I lived outside of Atlanta--more than two or three hours away. One drill weekend we were to have a Class A uniform inspection, so I brought my uniform and garrison cap. Well, our battalion S-3 had just been promoted from captain to major and bought a new service cap with the "scrambled eggs" on the visor, as field grade officers are entitled to wear. At staff call the commander said that we would be in garrison caps for the inspection but the S-3 protested--because he had just bought the new cover and wanted to wear it. So the commander said, "Alright. Officers in the service cap; enlisted in the garrison cap." Apparently every other officer had brought both types of headgear to drill...except me! I couldn't very well drive home, so I drove over to Clothing Sales and bought a new cover. After that I always brought along both caps when in Class A's--an expensive lesson. The beret solved this problem.