Microcontrollers
My first ever microcontroller was the Parallax Basic Stamp BS2SX, thanks to ads in the early-90s computer magazines I was reading at the time. Thankfully, both I and the industry have come a long way since then, but the BS2SX is actually pretty neat. I built a battery-powered wardialer using just it and some discrete components.
Cheat sheets for my current favorite microcontrollers:
The BluePill STM32F103CT8C6 board.
Espressif notes / projects / links: