A lot of good answers in this thread. I'm actually appreciating the lack of sarcasm for the most part.
Not because I'm bitter, but because this is the only place I get to talk mma, and I appreciate some intelligent talk from time to time.
Anyway, here's my top 5:
5. DHC: I think the Cub fight showed us all we had to know about this killer. Not only was I impressed with his chin, but at the ferocity at which he still came at Cub with after being hurt. Amazing chin, and recovery. A future just bleed Saint for sure.
4. Frankie Edgar: The little Frankie that could! This guy has fought nothing but killers for over 9 year's, and could only ever be put on queer street, but never finished. What makes Frankie truly great is not only his chin and recovery, but it's resistance across weight classes and a variety of opposition.
3. DC: Getting a little lazy here, and I'm high, but anyways..Champ Huge balls! Just like Frankie, DC's chin has held up across weight classes to tough opposition. Falling only to P4P king Jon Jones.
2. Jon Jones: Can't even remember him being rocked. This is against the highest level opposition available.
1. Jon Linekar: This guy ate shots from Jon fucking Dodson like they were m&m's. Didn't even flinch. Savage.