Scarab Mark 3 Assassin Droid

Mark 3 Assasin Droids or more commonly known as Sleeper droids were created by the Sienar Intelligence Systems. Held aloft by three repulsorlifts, armed with a stun blaster, a dart launcher, and an electrically charged covering, the Mark 3 was designed to capture, through nonviolent means, its prey. Because of the Republic's laws against assassination droids, Marks 1 through 2 were outlawed and so were most commonly used by bounty hunters and Separatists to kill a programmed target.

Source

 * Ulitmate Adversaries Sourcebook