Hi,
Actually, according to the product selector on Microchips website only 18 out of around 375 models (which are in production) is missing an internal oscillator of one type or another. They are:
Code:
PIC16F54
PIC16F57
PIC16F716
PIC16F59
PIC16F1454
PIC16F1455
PIC16F1459
PIC16HV540
PIC16F818
PIC16F819
PIC16F72
PIC16F73
PIC16F84A
PIC16F74
PIC16F76
PIC16F77
PIC18F6520
PIC18F8520
So it's close but not quite all ;-)

/Henrik.