Darth Chaltab said:
For example, I once had a player who loved to check for traps where there weren't any. She kept insisting on searching for them even in empty hallways, so I decided to humor her and made a really obvious bear trap. And when she tried to activate it with a bullet, I had it explode like a land mine just to annoy her. It was fun. :)

One of my friends use to do stuff like this all the time whenever we played. We once found what appeared to be a well in the middle of the desert (think of a fully bricked water well). He insisted that there had to be something weird/bad about it and attempted to use every skill he had to discover what it was. He was finally forced to give up as the rest of the players started moving on in the adventure. The GM never made anything bad happen with it either. It was just there to be there.