There are so many. I'd either have to keep coming back to this thread as I keep remembering them or just give up now. However, One big turning point for me, in that I instantly learned to love hard rock and "the sound of electric guitars", was when I was only 7 and my Uncle bought me Kiss, "Destroyer" for Christmas. Like most adults, he hated them but he knew all the kids were into the whole makeup, demon & blood thing.
It began with that realy low volume background noise of a guy leaving his kitchen and getting in his car and you could barely hear the car radio. I remembered thinking that the album must be somehow broken and 'of course' I kept turning it up to see if what I was hearing was supposed to be that way. Then the Real guitar kicks in with a simple but low volume - building to VERY loud and very dramatic opening riff. It nearly knocked me off my feet and to this day, if the song comes on unexpectedly on the radio, I get chills and smile.
I'm Riffing. People usually stop me when I'm riffing. Or carry on without me. That's also an option.