The 8-bit MOS Technology 6502, launched in 1975 and later used in computers by Apple and Commodore, is available as W65C02S6TPG-14 from Mouser Electronics.
Designed by Western Design Center (WDC), the processor is pin- as well as software compatible to the original 6502 and runs at up to 14 MHz. Its ancestor topped out at 1 MHz. Mouser says the 65C02 consumes about 300µA at a clock speed of 1 MHz. Mouser also offers an IP core of the 65C02 for use in FPGAs.
The 6502 was originally a spin-off of Motorola's 6800 processor, which was initially rejected by customers as being too expensive. Compared to the $300 price tag of the 6800, the 6502 sold for $25. Mouser offers the 65C02 for $6.95 today.