One of the most satisfying jobs I've ever done (And got paid $0 for it

Several months ago my dad bought the new corolla hatch, and of course, upon taking delviery the salesman was upselling him the dealership paint protection (lol) for a couple of thousand dollars. Told him specifically don't get it as it's a total ripoff

Offered to coat the car for free and it's the most satisfying coating job I've ever done in my whole detailing career. It truly felt amazing. Enjoyed every single second of it - even more than the high end Bentleys or Porsches 

What are the most satisfying jobs you've done?