I got scammed once, when buying a Nokia N900. But, that's not really an actual purchase in the end.
Otherwise, it's just a ton of stuff, that I've never really used. My high-end TI calculator is probably the worst in this regard. Nobody told me theoretical computer science doesn't require actual hands-on calculations, unlike engineering.
Although, when look back, my first thinkpad, T40 (still IBM), was a PITA. I got it second-hand from some guy and didn't do my homework. One of two USB ports turned out to be defective, and that model had ATi Radeon GPU, that was infamous for cold solder joints issues. I eventually ended up spending too much time trying to bake the mobo. It was an useful experience though.