There are dsPIC33 and PIC24HJ which have 12bit ADC.
ATxmega and AVR32 from ATMEL have 12bit ADC.
I don't think there's any microcontroller (at least not within my knowledge) with a 16bit ADC.
You can use an ADC chip if you need 16-bit, but I don't know of any 16-bit ADC with parallel output.
Tahmid.