The Holy Grail?
View attachment 498950
No.
Understanding stop shots is a fundamental part of learning pool, but it is not even 1% of the game.*
Stop shots are very useful for drills and for working on specific flaws in fundamentals. As Fran mentioned, you can do a stop shot with sketchy fundamentals, but if the practice is set up right, those flaws can be exposed.
I do not consider stun shots to be stop shots. You could call them "stop shots at an angle" but on a stop shot the cue ball stops. Dead. No movement. Stun shots have an angle but no draw or follow. Stun run through and dead draw shots (from snooker and carom, but used all the time at pool) are not stop shots.
As for the most commons shot, I think it is a smoothly rolling cue ball with no side spin. You must be able to accurately predict where that cue ball is going to go -- if you pocket the OB and have smooth rolling on the cue ball, the precise direction of the cue ball is determined.
Of course the most common shot depends on which game you are playing and your playing style. At nine ball you may find outside-with-draw or outside-with-follow to be the most common for some players. A couple of years ago at the Mosconi Cup, one of the things the European team did a lot better than the US team was to use no cushions when running a rack of nine ball. There were a lot of dead draw, stun run-through and dead draw shots but not that many true stop shots.
* 87.1% of all statistics are made up.