There is always an odd use for a timer.
I once wired a simastat (think electric cooker element control) into a mates house light circuit when he was away on honeymoon. He got back at night and turned on the lights. They when for 30 seconds and then turned off for 30 seconds, only to do it all again. It took him all of 1 minute to guess who had done it. We were always playing practical jokes on each other.