Simunition
this was a specialized form of ammunition that was created for the training of the clone troopers produced on Kamino for the Grand Army of the Republic. Combat instructors were forced to recognize that they had just a few years to get the clones ready for combat, and took advantage of technology whenever possible. Simunition was essentially pretend ammunition, so it wouldn't permanently harm any individual it hit. However, it delivered a nasty hurt when it struck, so that a clone knew when it was hit. By using simunition, combat instructors trained the clones to shoot their weapons instinctively, rather than by relying on targeting technology.