Ttgo Esp32 module with LCD (or was that an OLED?) is my go-to solution for one-offs and quick prototypes. Previously it was stm32, but I found myself fiddling with inconsistent SDK (ST's HAL) and myriad of configuration options for peripherals a lot more than when using SDK. The screen is also useful for debugging info (what's the IP of this device? what is the current state of inputs/outputs?).
So far I've built controller for x-ray tube (turning AC on for required number of cycles), oil boiler consumption monitor, gate/garage door opener (to remotely open the gate for delivery courriers), remote power and monitoring for electrical boiler for sauna and some more.
I'm using the teensy for a bunch of keyboard projects and having a blast.
On the other hand, FPGAs have warped my sense of what is possible though. Allocating s corner of a chip to one role and having other areas do other tasks at the same time with no context switching (...because hardware) gets very addictive.
So far I've built controller for x-ray tube (turning AC on for required number of cycles), oil boiler consumption monitor, gate/garage door opener (to remotely open the gate for delivery courriers), remote power and monitoring for electrical boiler for sauna and some more.