This trap consists of a long bookshelf along one wall in a room that the PCs expect to have a secret passage. One book is particularly incongruous (Courtship rituals of the lesser Mozambican gerbil) and sticking out from the shelf slightly (Perception 13 to notice). If pulled, it causes the entire ten-foot-tall bookshelf to slam forwards onto the ground within 10′ of the wall on which the shelves are mounted. (Perception 23 to spot the hinges and possibly some very faded bloodstains on the carpet; DC 23 skill check to disable the trap or set it off slowly; in PFRPG, 6d6 bludgeoning damage with Reflex 23 to take no damage, or 20 for half damage; in M&M3E, a bludgeoning attack with a +13 bonus.)
The trap also covers the real secret exit – a trapdoor which is now under the bookshelves. (DC 28 to notice it before this, as it’s under a rug.) If through some incredible fluke a PC is standing on the trapdoor when the trap hits them, the trapdoor takes as half much damage as the PC, and if that exceeds its 15 hp, it collapses under them. It’s up to you how far they fall and what they find.
This trap tends to work better in a modern setting, where sliding glass doors are more common and therefore less jarring in flavour. The rules text is for Mutants & Masterminds 3rd Edition.
The default trap is more humiliating than damaging, making it better suited to a consciously pranksterish builder, but by altering the nature of the door it can be made more lethal.
The trap consists of a sliding door with a clear panel, most likely glass but perhaps a monofilament mesh or damaging forcefield; the PCs approach it from a dim room, and the other side is bright, to ensure there is no reflection from the glass (or other medium). A DC 20 Perception check may be made to notice the narrow doorframe; this is slightly thicker against one edge of the doorway, where there is also a handle to pull to slide the door open. Initially stiff, it gives suddenly, and slides swiftly and smoothly along a groove in the floor and into the wall.
Unfortunately, the door is only part of a larger sheet of glass, and sliding the door across simply moves the other half of the glass into the doorway. This half, however, doesn’t have a mock doorframe, so the Perception check to notice it is DC 30.
Hopefully you’ll get PCs with both sides of this trap, and for an extra twist you can always put some gas on the other side for when they finally break through.