This is a hard choice, as over the years there have been so VERY MANY good ones.... but it is hard to forget the enema that led to my first ejaculation, around age 15 or 16. Yes, I was late to the party... perhaps because sneaking solo enemas every chance I got did take a lot of the edge off of developing sexual urges, even without ejaculation.
I looked forward to the "private times" when the house was empty to take a "big enema" with the family bag, but usually my urges were met using the easy to hide l'il 4 oz red bulb that had been my "go to" since I stopped crying when Mom squeezed it into me before age 6, and I started sneaking it to get more enemas than I could wheedle out of Mom. By mid teen, I had begun using the bulb in the bathtub, lying face down in a shallow amount of hot water, and inserting the bulb by working it down under me and slipping it in, then squeezing the bulb between my thighs to inject water, a li'l squirt with each thigh squeeze.
All I knew was it FELT GOOD... no idea what else it was stimulating, but of course I was hard, always was when the enema stuff came out. This time it felt EXTRA good, so I kept at it until suddenly I thought I was DIEING.... breath puffing HARD, heart POUNDING, all kinds of things happening inside that had never happened before. Eventually it subsided, I was still alive... and finally realized that I had just jerked off like the boys in school had been talking about. Well, maybe NOT how they had been talking, but the end result the SAME... or even BETTER! It was not long before I took that bulb into the tub again...and again ... don't care if I DO go blind. LOL
I still do enjoy the happy endings that enemas can bring, but that first one is still quite unforgettable. :-)