The MSP430F1xx - 1 Series have an 8MHz CPU delivering ultra-low power performance.

Upto 8MHz CPU speed
1.8 to 3.6V operation
Up to 60KB Flash
Up to 10KB RAM
Wide range of high-performance analogue and intelligent digital peripherals
5 ultra-low power modes of operation
0.1μA RAM retention
0.7μA real-time clock mode
200μA per MHz active
Fast Wake-Up From Standby Mode in < 6μs

MSP430 Microcontrollers, Texas Instruments

The MSP430 Platform is a range of mixed-signal, ultra-low power microcontrollers from Texas Instruments. The 16-bit RISC architecture is perfectly suited for wireless, low-power industrial and portable applications. This established range has a strong and popular position due to its ease of use and broad suite of development tools and support.
The MSP430 portfolio consists of over 400 devices ranging from the MSP430 Value Line to the revolutionary, highly integrated microcontrollers with embedded FRAM memory.This broad family of products offer integration suited to many designs and applications. High-performance peripherals include USB, RF, LCD controllers and Sigma-Delta ADCs. This allows designers to find the appropriate MSP430 device for many low power applications.