Randomize values just in one direction, e.g. for a flickering exposure effect

This expression creates a flickering effect on a layer - similar to a flickering neon light.

Film Burn is an Animation Preset that automatically creates the overexposed "roll-out" effect, where the tail (and the head if you want) of a clip flickers into overexposure. By Stu Maschwitz

You know the good old movies shown in an old flickering and not very well timed film projector where you can see the different frames scrolling.