Boss at my old company was hot on making people lock their machines. Used to leave notepad windows open saying "lock it" or similar, even when we had just gone to the other side of the room and could see him doing it.

After the Nth time of him being hypocritical and leaving his own machine unlocked when he went out of the room I made a scheduled event that popped up with "update complete, rebooting" and then restarted his machine, set to run randomly once a day between 9-5.