Mine was a 1978 Chevy Nova with a 305 and a 4-speed. The engine was okay, but all that smog bullshit on the engine made it suck gas like a 455 Olds mill.
Or maybe it was the tranny that kept the small V-8 running at 3,000 RPM at 70 mph.
The absolute worst part was the body. The paint looked like it had been put on with a paint brush and started flaking off in huge chunks about 3 months after I bought the damned thing new.
When I sold it after it had been totaled (a friend of mine was driving and a truck ran over the right rear quarter panel), some guy bought it from me and rebuilt it. He said he could have taken a feather duster and broken the damned car apart as the rust had just about obliterated the internal body parts.
HEY!! I got 18 mpg out of an Olds 98 I used to own as long as I kept my foot out of the secondaries!! It had that WONDERFUL 455!!
The worst car I ever owned was a 1979 Datsun 310 GX, at least mechanically. First thing to go was the shifting fork in the tranny. That happened just AFTER the warranty expired. Then I had to do some work on a head gasket. THEN the tranny went out. Finally, I gave it to my Ex when we divorced because it was paid for and got great gas mileage.
I wouldn't mind owning another, but only for the gas mileage. Through Texas & New Mexico, I was getting 37 MPG on a trip from Norfolk, Va to San Diego, CA. At least I know how to work on them now!!