Stupidest thing?
New Volkswagen GTI with performance upgrade, and a stage 1+ ECU tuning upgrade. Total cost probably around 30k! It is a lot cheaper than what you would spend on an Audi with the same performance, 40-50k. Oh, and with the upgrades all new tires, new brakes, and fuel(premium) would cost more as well.
I won't do it, but that doesn't stop me from looking.
Current car: worth about 4k, no loan, no collision or comprehensive insurance(just liability), decent gas mileage(30 highway), and somewhat fun to drive.
Anytime I consider a new car I do math, and math tells me how much longer I would have to work as a result... and then my little car becomes the greatest car on Earth. :)