The Vaccine Program Gun (ワクチンプログラム銃 Vaccine Program Jō) was supposed to turn Decepticons into Autobots. It kind of backfired.

Fiction

Micromaster

Sireen developed the Vaccine Program Gun, basing it on the cure he and Joe developed for the mind changer virus. When Sixliner fired it at Sixwing, however, not only did the weapon fail to work as intended, but it had the unexpected effect of turning Sixwing into Berserker Sixwing, powering him up and having no apparent effect on his behavior. Enter the Decepticon Sixwing!!