Although a survey of PGA tour caddies in 2011 revealed that half of them had witnessed instances of cheating, evidence of cheating in golf is hard to come by, so this is a rarety. Simon Dyson, an English professional golfer was playing in the BMW Masters in Shanghai in October 2013 and, when marking his ball on a green, noticed a 'spike', from a previously marked ball, and, when removing his ball from the green used it to push down the spike, thereby 'improving his line'. In other words, giving himself an easier putt to the hole. Nobody appeared to notice anything and he handed in his score card at the end of the round. However, a TV viewer did notice and informed the tournament organisers, who reviewed the video and agreed that Simon had contravened the rules. Basically, touching the line of his putt is not allowed as it could improve you lie or line of putt.
Simon was in breach of two rules, one for improving the line of his putt, which has a two shot penalty, and signing his card without taking account of this two shot penalty, therefore recording the wrong score on his card. It was this second offence that resulted in Dyson being handed a suspended two-month ban from the European Tour and a fine of $49,000.
Contrast this with the amount of blatent cheating that goes on in other sports and you can see how 'gentile' golf is in comparison!