I had accidentially left one of those corkscrews that has two tines on it in my computer bag. The security screener saw it on the x-ray (which means countless others didn't see it), pulled it out and asked me what it was. After I explained that it was a corkscrew and described how it worked, she shrugged her shoulders and put it back in the bag.

Needless to say, it's in my check-in bag, now.