A place I used to live near has WILD MONDAYS! They lower gas by 7 cents a gallon on Monday. It forces the station across the street to do the same thing.

And they suck you in with it--I made a point several weeks in a row of always getting gas on Mondays...until I realized that due to traffic patterns, that station is a pain in the butt to drive in and out of, and I was saving 77 cents a week.