Curious to know what are your rules modifications. By terrible house rules I mean things like collecting money on "free parking", limiting trade or not auction

Curious to know what are your rules modifications. By terrible house rules I mean things like collecting money on "free parking", limiting trade or not auctioning unbought property. I have yet to see commonly practiced house rules that improve the game. I am sure there are, but most people who know enough about game design to actually improve on the game typically don't play Monopoly.