2009 Toyota Camry Hybrid 4dr Sedan (2.4L 4cyl gas/electric hybrid CVT)
In the daylight, it works like an ordinary mirror, but at nighttime it works like a strobe. In city driving each time you pass a lit sign it decides whether to darken or stay in daytime mode. There's a lag time in its transformation, resulting in blinding light reflecting in your eyes when you pass a sign, followed by the mirror darkening, then going back to daytime mode just in time for the next lit sign, thus blinding you again. On the highway, when a car is directly behind you the mirror stays in the nighttime mode, when that car changes lanes the mirror switches to daytime mode and you're blinded by the next car until it gets close enough to activate the nighttime mode.
Steering control radio volume (because radio control sporadically doesn't work).
A way to lock the rearview mirror on nighttime mode. A way to turn the smart key off and have a regular key. The manual says only the dealer can turn the smart key off, but the dealer doesn't know how. The dealer and the manual shouldn't give conflicting advice about required maintenance.