The Airbus system.
Each sidestick has a takeover button. In normal flight, simultaneous inputs from both pilots will be summed algebraically, but priority will be given to the pilot who depresses, and holds depressed, the takeover button on his stick. A green light on the glareshield tells the pilot he has priority, while a red light tells the nonpriority pilot that his stick is dead. He can then retake control by depressing his takeover button. If he elects instead to release his stick, the green light in front of the priority pilot will go out. The priority pilot can then release the takeover button, extinguishing the red light and returning the aircraft to normal flight control.
If the non-priority pilot does not release his stick, however, because he is incapacitated, the priority pilot keeps his takeover button depressed for 30sec and then the dead stick is electronically latched. As soon as the obstruction is removed and the dead stick centred, it is automatically delatched.