Neuralizer

The neuralizer was a mind-altering device developed by Tabatha Brisk and Alexis Crimson, based on the work of Simon Van Gelder. Short for "neural neutralizer", this device used brain-wave manipulation to alter brain chemistry and stimulate paralyzing fear, rendering subjects extremely susceptible to conditioning, thus enabling a high level of mind control. Essentially, it "reprogrammed" a person. Stephen April used it to gain greater dominance over the crew of the ISS Arcadia and thereby prevent assassination attempts against him. It worked on most humanoids. (Star Trek: New Empire)