I was surprised to find out that the Marine F-35 JSF doesn't have a cannon. Seems odd, considering that it's a close ground support vehicle.
I guess they can put heavier caliber stuff on wingpods, but I wonder if the new doctrine is "bullets are obsolete, missiles are good, m'kay". If so, I hope it isn't a repeat the beginning of Vietnam and the Air Force (no dogfighting training, the assumption being that all fighting would be push-button stuff from stand-off distances, etc).