Consider the following trap:
Porcelain Doorknob Trap (CR 1)
A well-worn porcelain doorknob is in the center of the door.
Type: mechanical; Perception DC 17; Disable Device 17
Trigger touch; Reset None
The doorknob shatters, leaving sharp edges. Atk +8 melee (1d6 damage)
Sadly, this is a trap drawn from personal experience. The doorknob on my office door at home was stuck, when I forced it... well, porcelain is very sharp. Now, how can I use this in a game?
There is nothing really special or deadly about this trap; it is quite mundane. In fact, this may not even be a malicious trap, it may merely happen by chance as it did to me. This trap, though, has a purpose, especially if used early. It sets the tone.
A doorknob is a minor detail, as easily overlooked as any one of another hundred details - floorboards, tiles, bricks, etc. By turning a minor detail against the party, you enable your dungeon to become a living entity, full of rich detail and hidden hazards. The players, now alerted, will demand that extra layer of detail and attention that can bring an adventure alive.
Just be careful not to overuse it. Too many of these and the adventure will grind to a halt.
For more traps, please visit Trap-a-Day!