Jigsaw: Every Trap Ranked From Worst To Best
2. Shotgun Trap
There's a lot to be said for a trap that's effective in its simplicity, and that's exactly what the shotgun trap is. John Kramer himself is on hand to explain that Anna and Ryan are being punished for murdering a baby and causing a drunken car wreck respectively.
Jigsaw goes on to explain that there is a shotgun between them, and the "key" to this trap is the shotgun shell, which he then loads into the weapon.
Naturally they both assume that they must simply kill the other in order to live, but when Anna goes to kill Ryan, the shotgun backfires, killing her instantly. Ryan investigates, realising that the key to the chains was inside the shotgun shell all along, but the backfire has now destroyed it, leaving Ryan to presumably die of thirst in classic Saw style.
This was a classic Jigsaw troll, where the answer was hiding in plain sight, but of course, these poor saps didn't give it a second thought.