The recent West Indies-New Zealand Test match may have "swung" in the Kiwis favour because of a monstorous hit by Chris Gayle.
When I read the story I was reminded of a ploy adopted by the English bowlers in both Test matches. I noticed that the English bowlers were having a tough time getting the ball to reverse swing. Soon, Flintoff was repeatedly showing the ball to the umpires, supposedly complaining that the ball was out of shape. Twice (in both second innings, if I recall correctly) the umpires agreed and changed the ball to a newer one.
When the balls were later shown on camera, they did not seem to be unduly out of shape. (No matter how perfect a sphere a ball may be at the start of the innings, eventually the repeated contact with the ground and bat will cause a little bit of unevenness). I am convinced that this is a tactic adopted by them to change the ball if it is not helping the fast bowlers. I will be curious to see if they complain about the ball in the third Test match, especially if the Indian batsmen are on top.