I just finished Red Faction: Guerrilla (great game) and I was completing all the side missions. When I noticed I no longer had anymore side missions to do but it still require 6 missions for 'Revolutionary' unlock. Anyone have any ideas what the last 6 missions are?

I have no idea, i just beat the game then brought it back to block buster

Looking at a specific achievement's comment page is preferred to starting a thread.  The missions you are missing are most likely the randomly occurring activities you receive throughout the game, such as convoy and courier.  Good luck with this one.

The radio missions are completely random (and there are 28 in total), so there's a big chance you'll get a repeating one over and over as opposed to the ones you actually need.