Taking my grandparents for a fly. They had been flying with dad before and were supportive of his flying pursuit, and then I got to take them flying when I was able to take passengers. I think they'd be pretty proud of my achievements and where I am now with my career nearly 5000hrs later.
Yeah there's some cool stories of crap weather, dodgy aircraft and operators in the middle of nowhere, oddball pax and circumstances etc... But they don't make me as happy as I was taking grandparents (and many other very supportive family members) up for a fly, purely just for the fun of going for a fly.