Probably walking into the sporting goods store in my college town and finding the rifle of my dreams, a 1936 vintage Savage 99 in .300 Savage.
And, over the rest of that year, laboriously paying off that rifle with the proceeds of my campus jobs, to the point where, when Mom and Dad came to pick me up at the end of the year, we made a detour and I picked up the first gun I ever bought without needing Mom or Dad to sign for it for me.
And, pretty close to that was clearing my first round of wobble trap, 25 for 25, just the other year.
I've gotten close many times, but that was a great feeling seeing that last one shatter.