Not quite gaming but definitely classic computing:
Years ago my Dad acquired an executable file from someone that "was just too cool" (as he put it). He put the 720K disk into his 8088 DOS machine and ran the file. Suddenly out of the PC speaker came not beeps and bonks but actual music! And voice! It was essentially a commercial for a room deodorizer: the Magic Mushroom and it was compressed into an EXE "Realsound"-type file.
I think we played that thing like ten times it was so neat. I don't know when it happened but that sound file suddenly became a tradition whenever a new computer came into the house. Every machine until I moved out on my own all played "Magic Mushroom" before it ran anything else. Then the disk disappeared and we have no idea what happened to it.
It's been a while since I thought about the Mushroom until I was paging through the August 1989 issue of VG&CE. Access Software was announcing "Realsound", which was available for like three titles (Archon, I think, Leaderboard and a golf game). I was reading the ad to my wife when I started chuckling and I shared the Magic Mushroom story. Of course, she thought it was weird. Pfft.
According to Google this was a demo that was passed around to show that a PC speaker could do complex sounds. Does anyone happen to have this kicking around somewhere? I think my Dad would get a huge kick (as would I) if I told him to boot his 500 MHz machine to play that little chestnut.