FERROFLUIDS: Suspensions of iron particles in a liquid that form shapes when magnetic fields are applied.
* An iron door that is solid only through the grace of magnetism; turning off the field collapses it.
* Over here is a jug of some black oily material. Over there is a statue holding a detachable hilt that exudes an invisible magnetic field (going near, you feel the pull on your iron weapons and armor). Pour the jug on the hilt for a real Liquid Sword.
* Flicking the switch means that the slimy liquid at the bottom of the pit rises up and forms nasty spikes.
AEROGEL: Translucent, super-strong material that's mostly air.
* Cloudy glassteel pane: you can kind of see through it to all that treasure on display, but not break it.
* Or you can break it - but there's an angry air elemental inside.
PERFLUOROCARBONS: Breathable fluids imbued with oxygen.
* It's a pool with... a manticore at the bottom?
* I stashed my treasure under water at the end of this long tunnel. Suicide to try and swim, but only I know the water is breathable.
* Potion of water breathing - but you have summon up the guts to inhale it right into your lungs.
ELASTIC CONDUCTOR: Material that expands and becomes rigid when current is applied.
* Wizard's bridge over a chasm. You need to cast a lightning bolt to extend it all the way, but hurry - it only stays that way for a round.
* Curtains that part for anyone except the electric shock monster being held captive.
* Gloves that enhance a shocking grasp spell with a floppy ribbon that turns into a blade, adding stabby injury to shocking injury.
NON-NEWTONIAN FLUID: "A liquid that turns solid when sufficient stress is applied."
* "It's only a ten-foot drop, I'll just dive into this... AAAGHHH"
* You find a strange leather suit, that seems to be made of two layers with a little valve. Elsewhere you find a bottle of the fluid. It gives full mobility, works as plate mail against blows of all kinds, and can only be pierced by small soft scratches.
* The giant can walk on this water, but you little guys just fall through.
* Lair feature of a Great Old One wishing to outdo Cthulhu's non-Euclidean geometry.
TRANSPARENT ALUMINA: See-through (if slightly cloudy) metal.
* See above under glassteel doors and windows.
* Metal bikinis and codpieces just got more interesting.
CARBON NANOTUBES: Nano-scale fibers made of carbon: incredibly strong, electrically conductive, and yeah, the Cracked writer gets overwhelmed by the Cracked style guide at this point and just gets stuck on "bur bur bur awesome mind-blowing bur bur bur" so here's the WEBSITE OF A COMPANY THAT MAKES THEM, and the WIKI ARTICLE.
* +3 armor that looks like just a shirt and pants. Nanotubes.
* The beast with nanotube fur... equivalent to plate mail.
* A sword with an invisible blade. It's just one nanotube.
* The wizard installed some looong nanotube wiring in her castle to deliver fire and lightning damage to those below.