Seeing and hearing Karateka for the first time on an Apple II+ was a life-changing experience for me. Along with Ultima III, it made me want to be a game developer (I was in 4th grade, so around 12, at the time). Everything about the game is just so smooth and well-done- it has a plot, a progression, good animation and realistic sounds. I was pretty unhappy for years around the fact that I didn't understand the technology (machine language instead of BASIC, Apple's very funny graphics implementation, doing sound and animation simultaneously) to make games like that.
If anybody wants to see how that entire creative process went, there's a "game" called "The Making of Karateka" on Steam that is a nice interactive experience telling the story of Jordan Mechner's start in the games industry and how Karateka came to be.
It's a fun media experience with a lot of playable prototypes.