Mediation
Light switches are either 'on' or 'off'. Up and down don't make a flying fuck worth of difference either way!

A fabulously subtle trick to play on flatmates / family (only really works properly with co-habitees) is to turn all the switches upside down (they're usually reversable) and discreetly watch their confusion at the change.
(Greencloud Wanted to go fishing on, Fri 2 May 2008, 13:05, Reply)