OK maybe I'm a real "Geek" but the thing that attracted me the most to a Commodore 64 was the card slot on the back....

I would sit and "breadboard" home brew circuits and use a ribbon cable to control all sorts of things from the CPU.

Purchased a surplus Helium neon laser tube (Very expensive then, no such thing as a laser pointer yet) and use my PC to spin mirrors connected to motors...

Home brew laser show in the 80's.....

I remember the Atari, and the Tandy...

Bonus points if anyone can remember the exclusive dealer of Tandy PCs