I think someone mentioned this particular model needed the driver for customizing the LEDs.

Off the top of my head, non standard features could be

haptic feedback, vibrations, or purosely slowing the mouse down for interacting witha game

palm print reader

electric shock if the wrong person uses it

locking mechanism for a secret compartment

temperature sensor to let you know you might be sick

fan to kick in to cool your hand off if its too hot

persistence of vision display using the laser on the bottom

That's all I got right now, but the point is if someone wants to do something weird they should be able to.