Usually, I don't show my cards during a tourney. My opinion is, that they have to pay for seeing my cards. I also don't want to give any info about me and my bluffs.
Nevertheless I can't say, that I never showed my cards. Mostly if I showed my cards, it was in HU situations, especially when I had before a relative tight table image and I want to show a bluff or so, to make the oponent unsecure.
Rarely I was showing hands also with more oponents, but then only when I before was raising a lot and then to show a good hand.