My 4th round. It was a short par 3, and I stuck it 3 feet from the hole, and then dropped the putt right in the center of the cup.
I kept the ball, its in one of those ball stand things, it holds 50 balls, and I keep balls from meaningful shots/rounds. First eagle. First time breaking 90, 80, first hole in one, etc etc. Every ball is a nice memory.