Any kind of car parts outside of simple maintenance things like filters, hoses, etc.. Anything major like exhaust, alternators/starters, etc.. They never seem to last long, or they're not constructed properly the first time. For example, one of my exhaust systems I bought a long time ago wasn't expensive, but it wasn't necessarily cheap. Damn thing was molded wrong and it knocked against the sub-frame. And their high-temp paint coating melted instantly when I got the exhaust hot while toying with my car after I put it on.
Another fine example; I was in a pinch and needed an alternator. I had to get 4 before I bought one that actually worked. The other 3 would fry themselves right after installation.
The Greatest Respect You Can Earn is Self Respect.