An UNWANTED boner is one of the most embarrassing experiences a guy can live. That's why there are lots of "Viagra Pranks" videos on Youtube. Latin guys seem to be naturally gifted for this kind of prank (type the words "broma" "amigo" "viagra" into Youtube search bar and you'll see...).
Why am I talking about Viagra Pranks? First of all, because it's a very effective way to humiliate a guy, especially in a public place. Secondly, because I'm planning to write a story dealing with this topic. Stay tuned guys!