Bear trap
Example
DM:The orc across the hall starts mocking you.
Chris: well i go over there and kick his ass.
DM: as you step forward you activate the bear trap.
Chris: well i pull it off my leg and go over to kick his ass.
DM: no no no. BEAR trap. A dire bear falls from the ceiling. Roll initiative.
Chris: FUUUUUUUUUUUUUUUUUU