Had an experience when I was about 14 where I ejaculated within seconds of touching myself... almost instantaneously. I'll share that story at some point in the future.
So the poll question here is how fast you have cum... meaning from the time you first touched/stimulated yourself until you ejaculated. This could also included artificial stimulation such as vibrators... but not prostate stimulation. (I know... lots of rules. That's the way I do things.)