One of our freshly minted doctoral students just stopped by with his parents to tell me Thank You. He said that when he got here it was the first time he'd been away from his home country for any period of time, so lots of worry and plenty of trepidation. He said being greeted with a smile and cheerful "Good morning" and being wished a sincere "Have a good evening/weekend" as he left always made his day just a little better. His parents thanked me profusely for being a welcoming face each day, and that it helped him understand that Americans really could be nice folks. They were on the verge of tears and almost had me there, too.
Since I office at the reception desk I try very hard to be a friendly, welcoming presence. Having that effort rewarded with a genuinely emotional Thank You is about as good as it gets. Helps that I know it helped him, too.
Brad