You're a contract killer. Known throughout the world for your skill in some form of eliminating your target. Your method leaves no evidence you do not specifically leave behind, an M.O. if you will, which can be traced to you.
My weapon would be a small syringe filled with poison attached to my wrist that injected its contents into anyone whom I shook hands with. The gentleman killer. My M.O. would be leaving a right handed white glove on the chest of my target.
Alternately, a laughing gas that caused asphyxiation filtered through air vents or ducts.