I didn't actually land, but one time at the beginning of a long 6 hour
trek back home in a 172SP I did encounter an engine sputter. It was
really just a momentary dip in RPM, but out of the ordinary enough for
me to worry. I was climbing through maybe 2000 feet AGL when it
happened, so I decided just for safety sake to continue the climb, but
turned around direct back to the field. Checked the mixture, fuel
selector, nothing seemed out of the ordinary, and RPMs didn't fluctuate
at all again, so decided to return back to original enroute course.
Trip ended without it happening again.

--
Guy