My first donation still means the most to me: a hamper full of chocolates and a personalised card. That was back in April and I'll treasure it for the rest of my life. The fact that someone's willing to go through those lengths to say thank you is still mindblowing.
Since then, the project that I've been working on opened publicly for donations in November. We're going to hit 1,000 donations today, with ~$13,000 and close to ~$600/m recurring [0].
It's a massive motivator to keep going. The "thank you" messages and financial contributions have turned my time spent contributing to open source into probably my most emotionally fulfilling experience.