Has there ever been an aircraft with three sets of flight controls? On every aircraft I know, there is either one set of flight controls if it is single-pilot operated, or two sets of flight controls allowing either the pilot or copilot full control.

Has there ever been an aircraft that has three or more sets of flight controls?

To clarify:


"aircraft" includes fixed-wing, helicopter, powered lift etc.
remotely operated aircraft do not count.
A set of flight controls consists of yokes, pedals and/or sticks that allow the operator to manipulate the pitch, roll and yaw axes.
Depends if you are asking about production or testbed stuff, NASA had at least one test bed aircraft that looks to have had at least 4 sets of controls (also covered in this question). 

If you consider the space shuttle an aircraft, some of the thrusting capabilities (enough for pitch roll and yaw I belive) were operable from the arm control position.