Don't really think any of those mentioned have true 'Glass jaws'. Those guys, like them or not, are operating at elite world class level. They would not have got past the journeymen if they had glass jaws.

Best jaws I can think of:

Marvin Hagler
Julio Cesar Chavez
George Chuvalo
Jess Willard
Muhammad Ali
among others who I cant think of right now

Margarito has shown pretty good punch resistance through his career.

The trouble is, that when a fighter just 'goes' ...... their punch resistance seems to just disappear. We've even seen this from great fighters!

I'd like to see the Internet Warriors who are so quick to sit on a computer and call fighters fake, cowards, cheats, glass jaw etc take a couple of shots from a professional fighter to just 'recalibrate' their grading systems.