1d20 traps

Print PDF 1: icicle thrower, complicated convection system in the dungeon walls, freezes an icicle over a hour and then uses water pressure to launch icicle with great force out of a hole in the wall . Has a ten icicles on standby before it will need to stand down a hour to freeze a new one.
2: dehydrated bears: just add water for bears!
3:flying buzzsaws that ricochet around the room for 1 d4 rounds before shattering into shrapnel
4:300 bowling balls hurtling along the floor
5:flying squirrels covered in strong adhesive that latch on to your face, suffocating you in there skin folds.
6:Junkyard. Magnetic JUnkyard.
7:Fountains in side of wall narrow water flow to a thin very high pressure beam and grains of sand are poured into the flow. I.e a sandblaster. The pipe that shoots the water waves about crazily until it connects with something closer than the opposite wall. At that point it stops moving around and focuses on that point until it cuts through it
8.Sluice system to redirect underground river down corridor, smashing people back down the corridor and down a small drop, so they are pinned against a grill there.
9. Swing bridge is connect to bellows. Bellows pump air through a pipe organ that admits ultrasonic sound causing nausea, disorientation and fear. One person crossing the bridge give the organ enough air for 10 minutes
10. Damp corridor with dripping ceiling. In with the dripping water is a strange substance, while not poisonous per say, the smell of it makes horses become berserk and  fleshing eating.
11.Green slime. Actually colour altered naphtha so throwing a torch on it makes an explosion. 
12. Statures. If touched they immediately collapse into a cloud of dust. And it's asbestos .
13. Greased corridor. A sharp tree trunk is loaded on a slide behind a hatch, that charges out sliding down the corridor smushing stuff. THen is wound back to the firing position via a chain. The pressure plate for it was actually around the bend you just past, and has a delayed fire mechanism depending on how hard its stepped on. Ie the hard you step on it the shorter the delay, presuming someone moving at a brisk pace is placing their foot with more pressure.
14. Hall of mirrors! and its really hard going because theres a vent on the ceiling blowing strong wind at you. Its half way along the hallway and grit and stuff is getting in your eyes and its hard to hear. if its shut (cause it has a flap so you can) the air pressure builds up behind the "mirrors" which are actually just sheets of special treated (so it freezes reflective rather than transparent)  water and they prompt shatter 10 seconds later sending big sharp hunks of ice everywhere. Then the hatch will spring open again. Takes a hour for new mirrors to freeze.
15. Fluffy carpet on hall is super designed so you build up a huge static charge by the end of the hall. Then touching the door handle gives you a zap (shocking grasp) and that arm is numb for about half a hour.
16 Okay so its a room and there's a door on the other side. And when you enter the room it violently shakes and starts making omnious rumbling noises and gets really blindingly bright. And that door is actually just painted on. And then when you run to the door you came in you smack into the wall coz because the room the room actually turned slightly and there was a painting of the entry point (ie a black rectangle, because thats how it would appear from a really bright room.
17 grilled floor with bamboo shoots below. The present of light makes them grow really fast , coz wizards, (like 10 cm a second) and so you risk a sordid impalement
18 a lost kitten. Its really cute and lost and sad. It radiates magic faintly because of a deworming spell
19 Dart trap, but the darts are syringes that inject you with enlarge potions so you grow real big and start getting crushing in the tunnel. ho ho.
20 A helmet with a bag of holding inside it. Inside the bag of holding is a lot of staving rats. Inside the bag is a stasis field unless in the presence of intelligent being.