The recent 2018 Open Championship did not have many Rules incidents, but one is worth mentioning.
Erik van Rooyen played 18th hole Friday, and when he was preparing to putt, he dropped his putter on his ball-marker.
-> See a video about the incident (Facebook).
The question was, whether or not he may have incurred a penalty stroke. The answer to this question depends on whether or not a Local Rule had been introduced (as recommended by the Ruling Bodies from January 1st 2017), stating that there is no penalty in such a situation. If not, he would incur a one stroke penalty (Rule 18-2).
As in all Pro Tour events (and most amateur competitions) this Local Rule was in opreationTo his luck this Local Rule had been applied, and therefore he did not incur any penalty. By the way it was uncertain, whether the ball-marker had moved at all.
You can see a video below, where van Rooyen explains what happened:
He ended tied 17th.
If you want to read more about the Rules of Golf relevant to this incident (history and future), I recommend that you read this excellent blog by my associate Barry Rhodes.