Old news for many here perhaps, but here's a writeup about physicist William
Higinbotham's creation of "Tennis-for-two" at Brookhaven Labs in 1958:
http://www.cbc.ca/technology/story/2008/10/15/tech-games.html
Mentions how the initial inspiration came from reading the manual for an analog
computer and how it could be used for ballistic trajectory calculations.