How to use a TL431 for PMOS based reverse polarity protection?
10V zeners are quite nice devices for this application - quite sharp knee and far more accurate than required, not to mention cheap (only one part vs 3), and easily available. I can't imagine you would more than a couple types for any practical range of MOSFETs. Usually Vgs(max) is 20V, 10V or 8V, and usually the 8V types cannot handle your upper range of voltage. 

You can likely use a TL431 with a couple resistors, but I would suggest a Zener diode in most cases. The TL431 is an active circuit- it has this characteristic below the minimum current for regulation (the below graph is typical, worst case Imin is 2.5x higher- 1ma): 



The low current behavior of a 10V zener is far less non-ideal. For example, this nice SMT zener family (MM3ZxxxST1G): 



Even at a few uA they are behaving reasonably. 

The other "interesting" characteristic is the "tunnel of death" stability range: 



The MOSFET gate represents a capacitive load on the TL431 shunt regulator. Especially if you choose to use it at lower voltages than 10V you could run into stability issues at the edges with some MOSFETs at some temperatures. You cannot make a Zener diode oscillate, at least not so as you would notice it in this circuit.