Let's look at what 82games.com has compiled. First, here's their definition:
Game Winning Shot Opportunity = 24 seconds or less left in the game, team with the ball is either tied or down by 1 to 2 points.
And here's their timeframe:
So we're looking at five full regular and playoff seasons, with additionally the current 08-09 season so far.
Looks like Sugar Ray is pretty money. Not only has he hit 15 of 39, a percentage that puts him in the top tier. He's hit the third most in that time.
Pierce is shooting at a pretty good clip too.