Cricket

Cricket laws strictly state that any tampering with the original condition of the ball is wrong and unfair.

What does Law 42.3 read?

(a) Any fielder may (i) polish the ball provided that no artificial substance is used and that such polishing wastes no time. (ii) remove mud from the ball under the supervision of the umpire. (iii) dry a wet ball on a towel.
(b) It is unfair for anyone to rub the ball on the ground for any reason, interfere with any of the seams or the surface of the ball, use any implement, or take any other action whatsoever which is likely to alter the condition of the ball, except as permitted in (a) above.

Break the Law & this is what went wrong!

ACQUITTED!

John Lever-Vaseline Saga
In England's tour of India in 1976-77 fast bowler John Lever was accused of using Vaseline to illegally shine the ball in the Madras Test. Lever was using Vaseline strips on his forehead in order to stop the sweat getting into his eyes. Bishan Singh Bedi the then Indian captain, alleged that Lever was using vaseline to polish the ball, and thereby induce more swing. Later on, John Lever was not found guilty of tampering the ball.

Pakistan tour of Eng 1992-Emergence of Reverse Swing
In the 1992 tour to England, Pakistani fast bowlers Wasim and Waqar mesmerized the English batsmen with their prodigious swing with the old ball. The English camp had no clue about reverse swing then, and smelled something fishy about the swinging ball. Accusations were made that the ball was being meddled with, but no amount of hard evidence was found to implicate the two bowlers in question.

Ovalgate 2006
Australian umpire Darrell Hair charged a five-run penalty on the Pakistani side for tampering with the ball in the 2006 Oval Test. Pakistan retaliated by staging a walk-out. A huge uproar happened over this incident in Pakistan and the cricketing world was divided between the sub-continent countries and the others. Pakistan later on were acquitted of ball tampering at an ICC hearing.