I like when people are nice/friendly when there's no need to be.  It's kinda like getting good service. 

When I pulled up to the security checkpoint at work on Friday morning, one of the two nice guys checked my badge.  Both nice guys do several things to improve the quality of my life:  They say "Welcome to Happyland" or something like it; they greet me by name after they read it from my badge; and they say something like "Enjoy your day" or "Have a nice weekend". 

I'm not dissatisfied with the other badge checkers.  They say a greeting when I pull up, and they say a farewell when I pull away.  I'm ok with that.  It doesn't make my day any worse.  But whenever I go to one of the two nice guys, I always drive away with a smile.