Sand Timer Shenanigans: Scavenge a 3 minute sand timer from the game closet (mine is from Headbandz). Let's say the players are walking down a crypt corridor all La dee la dee dah. You inform the person on point that a stone they have just stepped on has made a "click" sound. Casually pull out the sand timer and set it on the table. It's time for your players to get their feces together. Suddenly, everyone has a limited window to decide what they're gonna do before two blocks of stone grind down trapping them, forever. Guaranteed excitement.