I'm designing a short adventure and running out of inspiration.
Had any memorable experiences with traps?
Any trap that is used in conjunction with bad guys. A pit trap is boring. A pit trap in a room full of armed and angry kobolds, carrying alchemist's fire to roast whoever falls into said pit trap... isn't. (Even nastier when the kobolds have a sorcerer who can slide opponents into the trap...)
A pocket of swamp gas in a sewer is boring. Make Endurance checks, someone fails, falls into the water and loses hit points/a healing surge. Someone blows it up, there's some singed eyebrows. *Yawn* Combine that encounter with a pack of otyughs (who are immune to the stench, because they eat stuff like that) and it can be used as a resource, PCs can blunder into it, etc. Naturally, the enemies who can do the same; just picture what a neo-otyugh (has the ability to pull enemies and has threatening reach and I believe grabs PCs) can do with that.
Also, wilderness hazards, as rogues simply don't go trap-hunting outside. Ranging from (no pun intended) a set of hidden bear traps that restrain the victim (a big deal, when the rangers who set the traps can now shoot them with bonuses) to nasty but immobile poisonous foliage which the bad guys know about (and avoid, but stand so the hazards are between the PCs and them). Bear traps can be replaced with quick sand, tar pits, and what have you.
I've only really used traps once in my 4e campaign. I need to find a way to use some outdoor hazards; I'm hoping my PCs go into a forest and ... well, some of my players might read here so I'll stop there. In that trap encounter, the PCs were after a planar portal which was letting demons into Athas. (Anyone who has read
City by the Silt Sea will be familiar with this.) The portal was itself a trap, which could push people down the stairs. The PCs had to go past two flights of stairs to get to it. The first had a pair of turrets, a fire AoE turret and a cold slowing turret. A dray/dragonborn templar kept roasting them as they approached, and his recharge power slowed them as well. The first PC to make it up the second flight of stairs (he actually skipped that, just using Athletics to pull himself up a level) found himself triggering the second trap, which threw him back down. Despite facing a single sentient opponent (the templar), the PCs were struggling just to move. Eventually they took control of the turrets and used them to blast the templar. The turrets didn't have the range to reach the portal though. Then the portal started summoning stuff...