On the challenging front, we can find the infamous expression: "what the f*** are you looking at?" or its politer version "what are you looking at?" There have been interesting stories around these episodes, usually defiant, but what matters today is the answer. I am looking at you. And the words unsaid. I am looking at your soul.
As years went by living in England, I was rather shocked in one of my brief escapades to Barcelona, where people do indeed look at each other in the eye all the time. It's the natural thing to do...