The Energon Prod is Knock Out's primary weapon. It can be used to electrocute enemies and seems to have multiple strength settings that can knock out, paralyze, and just plain induce agony in both humans and Cybertronians.
Three years later, he used one to interrogate William Fowler as to the location of the Autobot base on Earth. As he had suspected, Energon and human nervous systems did not mix. It had the side-effect of leaving Fowler completely and utterly incoherent.
Knock Out used an Energon prod as his primary weapon, electrocuting Optimus Prime while trying to capture the Energon Harvester, and later attempted to use it on Bulkhead. Bulkhead took it and used it on Breakdown instead.
Knock Out possessed a smaller prod in his vehicle mode, that he used to stop Vince from struggling after capturing him. It rendered Vince unconscious enough to not notice Transformer battles going on around him.
He later used the prod while assaulting a human military base.
Later still, he gleefully used the prod to electrocute and paralyze Cylas, mockingly telling him that, "Breakdown would be tickled", just before having him dragged away to his laboratory.
Starscream attempted to use an energon prod to force some compliance from Predaking, the beast having been left in his care by Megatron and Shockwave. Shocking the beast very nearly got him roasted in retaliation, so Starscream wisely changed strategies.
When Knock Out and Starscream accidentally turned Cylas into a Terrorcon, Knock Out attempted to subdue him with his energon prod. Cylas promptly broke it in half. It has not been seen or used ever since.