Probably the nerdiest camera app ever made, ca-mera uses a cellular automaton to interpret the brightness values of your camera stream. The resulting images are black/white and pixelated, and contain unique patterns created by the cellular automaton (Wolfram rule 126).
This app provides a "selfie" mode, and lets you change the appearance of the pictures by controlling the automaton application direction, the resolution, the input brightness, and the input fidelity (i.e. to which extent the cellular automaton is allowed to run freely).