What tools??
 

Other than roll pin and brass punches. What special tools do I absolutely have to have to build an AR??

I have an upper with no handguard, but other wise complete. I have a stripped lower, and a parts kit to install.

I'd say an AR wrench as well

An AR wrench, vice block and torque wrench if you plan to take off the barrel nut to install a free float tube...the AR wrench will also help installing a collapsible stock if applicable. Other than that just basic household tools like needle nose pliers, screwdrivers, hex nut keys and duct tape (to cover the jaws of pliers to avoid ascratches). I have also found a magnetized mechanics bowl is useful for holding small parts and from keeping the punches from rolling all over the work space.