Seeing snow falling under streetlights at night.
Dog smiles.
Butterflies.
Lightning bugs.
Car shows.
The feeling of "OK-ness" after 2-4 beers.
Discovering a new song or band you really like.
The smell of freshly cut grass.
The smell of rain in late spring/summer.
The feeling after a workout, especially when you improve.
When you get the hang of something you've been struggling with, when it "clicks" how to do something.
When you get a breakthrough idea, or at least a good idea.
And, used to be when we would all be together and sleep over at our house on a holiday.