I've printed on purpose before as well.
I was walking with my girlfriend on an old dirt road. A couple hooligans were throwing stuff off a rail road bridge about 500 feet from the road. When they saw us they said a few things then started following. As we walked they got closer and closer. So i light a smoke. And took off my jacket which i handed to my girlfriend. I waited purposefully for them to get within 15-20 feet or so, then i bent over and stubbed my smoke out in the gravel, thus 100% printing my full size 1911 through my button up shirt. They stopped dead in their tracks and i heard them say "yo lets jet up to jimmys" and did a 180 and walked QUICKLY away.
Luckily printing is legal in my state so i didnt mind giving them a non verbal warning.
I've also done the trick of sighing and stretching my arms WAYYY above my head in a 7-11 causing my OWB holster to show about 3" of the bottom to some really sketchy looking guys behind me in line......they left.