Turning on the flashlight with Siri
A quick dash round google gives me the impression that it could do it in iOS 7 beta 1, but the function disappeared after that & was never in a release iOS.
"Launch Flashlight" used to work. (You had to download one of the flashlight apps from the App store, as the command would not work for the default iPhone flashlight.)
Apple has now de-activated this convenient feature. Why? Who knows.
It was real convenient at night, with the iPhone charging on the nightstand, to simply get some light while in a dark bedroom - like when you wake up in the middle of the night because of a phone call, some noise, or just to go to the bathroom.