This is a great and long-running topic for obvious reasons. I think it is about time to tell MY story:
I was about 12 and hadn't "haired over" yet. We had forced-air heating system and you periodically had to replace the filters or clean them. My mother gave me the job of cleaning the filters. This was a boring job for a kid on a Saturday afternoon. My younger siblings were enjoying a Saturday afternoon movie on TV and my mother was busy with other things which is why she sent me to the basement to do this task.
Cleaning the furnace filters consisted or removing them, then using the vacuum cleaner to remove the thick layer of dirt on the outside. Bored kid, totally alone, unlikely to be disturbed. Singing vacuum cleaner. Sucking vacuum cleaner hose. Need I say more? After doing the task at hand, I started playing with the vacuum cleaner/hose, seeing what it would suck and/or stick itself to. After trying lots of things, I noted how it felt sucking my clothes, then my hand. Well, a light went on in my brain almost as if someone whispered the thought in my ear: What if I stuck that pulsating hose over my penis? I am not sure I started with an erection but sure got one in a hurry. I can almost still feel the sensations as the hose vibrated my penis, making the most interesting sounds (to a kid) as I moved it from total engagement to just on the head of my penis which it tickled in a high frequency dance inside the mouth of the hose. I tried sucking my underdeveloped scrotum/testicles with the hose but that didn't produce anything like the sensations that I was getting with my penis.
My penis/hose playing lasted probably 10 minutes. My heart was racing and the feelings in my pelvic area just kept building. Then the most incredible thing happened: This feeling started emulating from inside my body. It startled me. Then came the swollen feeling in my penis, like ti was going to burst, then the contractions from within. I immediately removed the hose to find a heavy, white, substance erupting from my penis. I was scared to death. What had I done to myself? Maybe something bad and I would have to confess to my mother what I had been doing and then to a doctor. But the feeling as the contractions from deep inside ceased was indescribably satisfying. What a roller-coaster of emotions.
Being a kid, I was naturally curious about the mysterious fluid. It wasn't urine or anything else that my body had produced before in my past experience. I felt of it between my fingers. It was mucus-like with a strange smell. But it also had the unusual quality of containing considerable sand-like grit in it. (I don't know to this day what that was all about. I would like to hear an explanation.)
Cleaning the furnace filters was a monthly task. I had to do it many times after that first ejaculation experience. The immediately following, I was reluctant to repeat the hose play but succumb again like the proverbial moth-to-a-flame. It was the same exact experience except a little less scary since nothing bad had happened to me after the first time. (The semen was again grit-filled but then the phenomenon ceased) So the scenario was played out many times after that. (It was predictably not as satisfying subsequently as that first time.) I didn't learn to whack myself off until much later. I think it forced puberty. I quickly developed pubic hair. A year later, facial hair started emerging. It was only at that point that my mother gave me a book about "the birds and the bees". I had been clueless until that point. I thought ejaculation was just something new for me to enjoy all by myself.
I wonder if I am the only person whose first sexual experience was with a vacuum cleaner? Somehow, I doubt it.