Accidentaly, once. I was a student and my CFI was doing a simulated emergency. I was a few hundred feet from touchdown and was going through the "just before you crash" checklist, that includes pulling mixture to idle/cutoff. Well, I pulled it just like the checklist told me to.

The instructor pushed it right back in and the engine started within a few seconds, but that was good enough for me.

We do have an instructor that pulls mixture on his students in the pattern. Not something that I would ever do.