My first was Atari BASIC on an Atari 800XL. I have memories of typing the "Monster Maker" from Dr. C. Wacko's Miracle Guide To Designing and Programming Your Own Atari Computer Arcade Games that was used to easily make 8x8 sprites or "character graphics" by POKEing to replace the character set in RAM.
I don't know if I'd call them fond memories. I remember my mother getting annoyed by the chirp the computer made every time you typed a letter and I learned a POKE command to turn it off, so that I could keep the volume on the TV the same for when I switched over the cartoons.