White Elephant (a.k.a. Yankee Swap)
Classic, but for a reason! This game exists in many versions, but this is the easiest one we've tried.

Each person brings one wrapped item, usually an inexpensive gag gift, but not necessarily. The host selects a random person to pick the first gift and unwrap it. Each subsequent person in the circle can choose either a wrapped gift or steal an unwrapped gift from another person (you must wait at least one turn to steal an item back). Finally, once everyone has a gift, the first person in the circle has the opportunity to steal a gift (since they had to pick from the unwrapped pile on their initial turn).

White Elephant Candlestick, $48, available at Macy's.