The question was framed like this :- what club affects your score the most? If I digest this a bit, it isn't literally what club, it's what part of your game? Or at least that is how I see it...You can chose what you hit off the tee, Driver, Wood or Iron. You can chose how to approach the green, but you really only have one club once you get to the green. Putter is king, one pro put it like this, the reason why we are irrational standing over a 4 footer is that there is no option B, no hope for an up and down having missed the green, no brilliant escape shot from the trees after your wayward drive, you either make it or you add a stroke - the finality is what depresses us. If anyone is still not convinced, just think about the last time you played with a guy who you and everyone else in your group recognizes as a truly gifted putter, just think how many times you've had to dip your fingers into your wallet to settle up with him after the round, maybe you'll see my point. For the record though, whereas I think I could work on my putting to improve it to average or slightly better, it would take perhaps supernatural intervention to sort out my driver.