One time I walked out of the restaurant, some guy driving by just yelled "Welcome to the USA!!!!" I am originally from Hong Kong. It was very random, thoughtful, and stupid.
I worked at a grocery store for about 5 years. There was this one really sweet elderly pastor who used to come in with his wife almost everyday. They were both well known to everyone at the store, very sweet couple. I ran into them while out with some friends at a restaurant celebrating my 22nd birthday. When I told them we were out celebrating my birthday they had the wait staff bring out a birthday balloon for me. For the next 2 years after they never forgot my birthday and would leave me a birthday card at the store with $10.00 inside. It was the sweetest thing for two people who hardly knew me to remember my birthday each year.