Season 7 was my personal favorite. It was one of the funnier seasons with laid back, talented fighters, minus that one douchebag (I think his name was Jeremy.) Out of that season there are still seven cast members fighting for the UFC, several on impressive streaks, especially Matt Brown and Gerald Harris.
Amir Sadollah was my favorite cast member from any season just edging out Tom Lawlor from season 8. I think he has a bright future in the WW divison.