The classic memory game Simon has been recreated in many forms using the Arduino development platform, with an almost infinite amount of variations with regards to the controls and outputs. However Jason Poel Smith has taken things further and created a two-player version that allows the end user to add their own control types for the buttons.
By adding sockets connected to the four inputs for the game, almost anything can be used that closes the circuit, from connecting a piece of fruit to actual people, using each person's head as a button. You might want to be careful with that example. A quick demonstration is shown in the following video: