NXP (http://ics.nxp.com/products/mcus/cortex-m0/ http://ics.nxp.com/products/mcus/cortex-m0/) and Energy Micro (http://energymicro.com/ http://energymicro.com/)

NXP (http://ics.nxp.com/products/mcus/cortex-m0/ http://ics.nxp.com/products/mcus/cortex-m0/) and Energy Micro (http://energymicro.com/ http://energymicro.com/) are actively trying to kill the 8-bit MCU with their ARM Cortex-M(3|0) offerings. Very low power consumption on these chips. But, still, they require a lot more external circuitry than an MSP430 or (SiLabs)C8051.