Battle Chess
Battle Chess, originally developed by Interplay Productions in 1988, gave every chess move a visual payoff: pieces walk across the board and fight each other with unique animations when one captures another. The rook stomps over pawns; the queen dispatches opponents with magic. Each matchup has its own animation, so part of the fun is seeing what happens when different pieces clash.
I was in college, two quarters from graduating, when my good friend Mike Morhaime asked me to contract with his startup, Silicon & Synapse (later Blizzard Entertainment). I worked on it part time while finishing school and working another programming job in the Psychology Department developing analytical software.
The contract was to port ("convert") Battle Chess from DOS to run on Windows 3.1, where I had some expertise already. I got paid very in monetary terms -- it worked out to around $5/hour -- but was paid handsomely in learning. I also gained the confidence to believe I could write games myself.
The part I couldn't get working was the music-player, which would not run well in Enhanced Mode: Windows CPU time-slicing was too slow so the music would stutter. (Everything worked fine in Real Mode and Standard Mode). I just disabled music.
The other challenging issue was getting a game that wants the whole computer to itself to run nicely on Windows, a cooperatively multi-tasked operating system, required some clever hacks.
I later developed the Windows-MPC (high-resolution 640x480) version, which looked quite good.