Dungeons and Dragons

Ben Milton's take on traps is, I think, the best way to handle them.

Don't use traps as a hidden thing. Make the trap itself obvious to the players, and describe it's positioning. The trick should be for the players to figure out how to either avoid or safely disarm the trap.

One example he uses is a pit trap with a narrow board serving as a bridge over the top of it. The smell of volatiles indicates that there may be some kind of fuel at the bottom of it. The board is on a rotating mechanism, and if anyone tries to stand on or otherwise move the board, it ignites the fuel below with flint inside the mechanism, like a lighter. Since the pit is too large to jump across, players will need to find another way across.

In my own game, I recently pointed out a section of floor filled with skeletons whose legs were partially sunken into the tiles up to the knee. Since the sections of the floor were too long to jump across, they tested what was wrong by throwing objects onto the tiles and seeing what happened. Once it was clear that only objects that had been stationary for a few seconds sank in, they sprinted through the hallway and made it to the other side fine (one character lost a boot). They had fun, nobody felt it was unfair, and I would call that a win.

Unfortunately for them, the floor on the other side of this trap was greased, so they went sliding down a chute to the fourth floor of the dungeon, and had to look for a way back up, which came in the form of a previously inactive elevator that was a shortcut back to the first floor.

Sen's Fortress in Dark Souls 1 is a good example of how traps like these can be utilized. They're all obvious and easy to avoid, and serve more as positioning puzzles than as gotcha mechanics.