I'd have to go with OXO. But I am highly biased since this is my favorite pinball.
OXO was the first truly great Williams EM with DC pop bumpers and sling shots. It was the first pinball machine that I played that had that feel of raw power but quiet at the same time. The pop bumpers are just awesome when working as they should.
It's got an awesome 'around the world shot' too, one of the best in pinball. Shoot the pinball up the left side lane, the pinball hits the 'A' target, flies over to 'B' target and then down the right side lane. It's a very rewarding shot when you accomplish it then hit the middle target to light up the red 'EXTRA BALL & 5000 WHEN LIT' kickout hole inserts.
The neon pink green, pink, red and blue colors are surprisingly pleasing and it's awesome when the marbleized green and blue pop bumpers and then the red inserts are lit. So much very 70's.
Quoted from bonzo71:OXO for the pointy people.
OXO is the quintessential example of Christian Marche's Pointy People. The Pointy People are a bonus!
OXO has so much going for it - and it's a four player. This, to me, is when Williams put it all together into one package.