- Adventure, developed by Warren Robinett for the Atari Video Computer System (later renamed Atari 2600) and released in 1980, is notable for containing the first well-known Easter egg in a video game, which revealed the designer’s name.
- SNDMSG (Wikipedia)
SNDMSG was an early electronic mail program, chiefly notable because it was used to send what is considered the first networked email.