Agreed with the posters above that I could probably list 20 experiences, but one recent one ...

Went (for the first time) to Bogota and had a fantastic time, but didn't get to see enough. A FA was sitting in the jump seat in front of me (obviously in coach) on the return trip, was originally from Colombia, and we spoke for quite a bit before service started about how great this city/country was and that I was coming back soon to see more.

When we landed, she gave me a Bogota city map (difficult to find) that she had gotten the night before, with some post-it notes inside on what/where I needed to visit next time. It was nothing more than an (incredibly) friendly gesture -- someone who loved her home country and her airline (we spoke a bit about Delta on the trip back as well). Luckily, I was able to dig up an "Above and Beyond" certificate, and also wrote a detailed letter into Delta. These are the people that make me continue to fly Delta.