Squillions of them. Microchip, Silicon Labs, Infineon, and Maxim all produce such µCs, like the Silicon Labs EFM8BB - up to 50MHz, a small handful of kb of prog

Squillions of them. Microchip, Silicon Labs, Infineon, and Maxim all produce such µCs, like the Silicon Labs EFM8BB - up to 50MHz, a small handful of kb of program space, a smaller on-die RAM, off you go. Or pick a more specialised IC like the Cypress FX2LP family of USB controllers - they embed an 8051 core so you can apply firmware using cheap, widely available tools.