I remember as kid, playing the Zork series and exchanging hints with my 4th grade teacher. Great game, and that made it all the more fun.

I think the game that had the biggest impact on me, though, was a game for the Apple ][ called "Odyssey"... I remember many hours lost to that game:

http://en.wikipedia.org/wiki/Odyssey:_The_Compleat_Apventure