Another vote for Black Knight. It wasn't the first pin I played, but it was the first one I remember being really different and cool. It also was the first pin to really piss me off. Most of the games I remember from back then were EM's that gave you 5 balls for a quarter. The bowling alley my folks bowled at on Sunday nights got a BK and I thought it was the coolest thing ever - the sounds, digital displays, multilevel playfield, etc. They'd give me money to go play so I wasn't a pain in their ass. Then I finally got to play it. Dropped in my quarter and nothing happened after my 3rd ball drained. I was livid. I thought it was broken. Or a ripoff. It wasn't fair! All the thoughts racing through 7 year old me's mind. It was the first 3 ball game I played. I promptly went back to them and begged for more quarters.
Years later one of my friends from work who collected pins got a BK. I realized 20 some years after the fact that it's not the easiest game out there.