I have used the "Harvard group test of hypnotic suggestibility" (slightly modified) on classes from 15 people to 250 (university-aged), when we talk about consciousness, or when we talk about Mesmer (separate class). Anyway, I get a nice normal distribution of people who are not at all affected, through people whose hand raises on its own (on my suggestion), those who hear a noise, feel a fly on their nose, etc...up through a very few who see me as invisible (or don't see me, I guess), and 5% or so who respond to a simple post-hypnotic suggestion.
I have had people who did not believe in hypnosis go under (never anybody who did not want to), and I have had 2 people who, in the course of discussion afterwards, went under immediately when I snapped my fingers. (oddly enough, I was not suggesting that--it appeared to be what their expectation of the situation called for).
After the demonstration, we end up with some people believing it's real, others believing it's bunk. My own opinion is that it is nothing magical, just a powerful set of expectations for how we should act. When Mesmer zapped people, they flopped around. Nowadays, they seem to fall asleep (sorta). Same process, different expectations, different results.
and no, I've never been hypnotized myself--closest was while watching another induction, the hypnotist said "as I count to 10, your legs will feel heavy", and damned if they didn't do just that! But then, yawning and itching are contagious too...