Most stable internal microcontroller clock
Based on your comment that you want 1ms error maximum in 4 seconds, I would say that no microcontroller has an internal RC clock that is that accurate under typical operating conditions. +/-0.025%. 

It's also probably too tight for a ceramic resonator (more like 0.1 to 0.5%).  

On the other hand, it's well within expectations for a typical inexpensive crystal, but if you want to be really sure you can use an external oscillator, which will be guaranteed over temperature and for initial accuracy.