If you ask me... (Which nobody did) Derived from Thomond2006's list, in case you couldn't tell.

IMPACT PLAYERS

New Zealand: McCaw, Carter, Nonu, Williams, Reed

Australia: Pocock, Genia, Cooper,  Beale

SA: Matfield, Morné Steyn, du Preez

Ireland: O'Connell, O'Driscoll, Bowe

England: Croft, Flood, Youngs

Wales: Hook, Shane Williams, Adam Jones

Scotland: Gray

France: Harinordoquy, Trinh-Duc, Medard

Italy: Parisse

Argentina: JM Fernandez Lobbe, Henandez (If he's fit)

Samoa: Mapasua

Some players, such as Adam Jones, have been added for one outstanding atribute, in this case, his scrummaging. He has a huge impact on the game, but not every time he touches the ball.