Depends on what it is, who it is, where it is, and whether or not the person is armed. I mean I most likely wouldn't be telling off a bank robber, but a friend stealing my gum?
Hm.
I would most likely just get on my knees at put my hands behind my back and say: "I surrender!" and then they'll be like; "Wth?" and maybe,if I'm lucky,they'll put the stuff back :B.