[Trap] A twist on the classic pitfall

Place this in a narrow corridor or at a choke point.

Standard hidden pit with whatever nasty you choose to put inside. Make it a bit easy to find, something to make the PC a bit confident that they're good to go.

Make the next block a secondary trap with a tripwire, a pressure plate, a magical PC detector or whatever. The secondary trap, when tripped, bull-rushes the PC back into the pit via whatever method you like. Maybe a raging bull statue slams into the PC, a log swings down from the ceiling, a magical force foot punt, whatever.