Three Traps

Trap Number One: 

“The walls, floors, and ceiling of this room suddenly shift from worked stone to flat metal plates, and a barely perceptible hum fills the room. Only one exit exists, directly across the room. It is guarded by a single near-naked barbarian wielding a nasty club decorated with a human skull.”

Any adventurer wearing armor or using metal weapons who enters into the metal areas will discover that the whole room is a series of electromagnets, with polarities shifting every other turn to the left/right/ceiling/floor (or roll a d4 for the side). 

The barbarian is just a combat threat to make the trap more dangerous, and can be replaced by any orc/ogre/naked and dangerous person not using metal.

How to Beat Trap One:

Might: Pass a hefty strength check to resist and move across the magnetic plates. Or strip and challenge the barbarian to unarmed combat, tying a rope to your gear and dragging it across afterwards. Try to lift one of the wall/floor plates so that the trap breaks/crushes itself under its own power.
Cunning: using ball-bearings, Chainmail rings, looted gear, etc, wait until the magnet activated on the ceiling and try to use sabatons or iron-shot boots to dash across to the door before it changes to the floor and bypass the enemy.
Skill: Try to get to know and/or persuade the barbarian into letting you pass. Try to deceive the barbarian to hold something metal just before the magnets switch polarities to another wall (“Catch!”). Try to dig quickly under a plate to disable the magnet by throwing coins/water into the spinny-bits/batteries.
Magic: Use any electrical spell to short circuit the electromagnet trap. Use Create Water to try and flood the room. Use Charm Person/Monster to get the barbarian to let you pass. 

Trap Number Two:

“A series of standing mirrors in this room are spaced at regular intervals, blocking the view of the room and corresponding to the points of an angular mandala. The room is lit by an eerie pink glow. “

In the center of this room sits a stone column marked by three rubies down two sides. One side has an open eye and the other a closed eye carved into the stone. The gems are shooting deadly lasers into the mirrors creating a geometric prison guarding the heart of the trap. The lasers are at the six, five, and two foot heights. The mirrors are bolted into the stone floor, and only are mirrored on one side. The lasers shoot out of the open eye and into the closed eye gems, perpetually charging itself. Arcane deduction should inform players that make it to the center that removing the closed eye gems first is safe, removing the open eye gems first will have explosive results. 

The exit to the room can be on any side, but is blocked from view by the mirrors.

How to Solve Trap Two:

Might: Tear a mirror from the floor and use it as a shield! Direct the lasers at the mirror’s unprotected backs and shatter them with the laser! Or use it as a shield and open doors for you and your party!
Cunning: Use a hand mirror to stop the lowest laser, letting you and your party crawl through the lowest level. Break a mirror and watch the lasers annihilate the other mirrors a chunk at a time as they shoot in fractal patterns.
Skill: Use acrobatic or athleticism to hurtle or gymnast your way through the lasers. Climb atop the bolted mirrors and step-stone your way across the room. 
Magic: Dispel the center of the room. Cast darkness on the center of the room. Use your familiar to fly or crawl to the central pillar and remove the gems. Overcharge the pillar using a fire or light spell. 

Trap Three:

“The long hall stretches in front of you, lit only by your own torches. The floor ahead abruptly ends in a yawning pit, but a metal trunk stretches to what appears to be more floor on the other side, and something low lying on the floor across the way. The trunk below shines with an oily sheen, and from somewhere above, fresh wind makes your torch flicker.”

This is a simple pit trap consisting of a fall to doom and a greased metal pole, complicated by some air ducts that push characters off as they cross. Canny players may ask about the ladder stashed on the opposite side used by the dungeon denizens to cross safely, but retracted when defending from marauding drunken slayers and brigands. 

How to Solve Trap Three:

There are a myriad of ways to pass this trap, but for this one, let your players figure out how they want to make their way across. How will they solve it? Ask them to describe how, not just roll a dice to figure it out. The game is always more fun when everyone participates!