Most have been mentioned.
Ralley wheels on post '69 cars.
Pistol grips in pre '70 cars.
High impact colors on pre '70 cars.
People trying to make their '68 Coronet look as good as a '69 by adding N-96 scoops or side scoops to it.
Steel wheel/dog dish caps on EVERYTHING, especially by the purists that complain about cars with non-original parts on them.(Then stick on steel wheels that didn't come on the car)
Complaining about chrome magnums on cars instead of Road Wheels. This goes along with the folks that believe that you should keep 14" tires on the cars so they can not hook, not handle, be slower than a Honda accord and stop 10 feet shorter than a 3/4 ton pickup that weighs twice as much.
Rows of A-12 cars that are all nice and proper with the same boring steel wheels on them that just drive from heated garage to enclosed trailer to show field to enclosed trailer to heated garage. Factory street racer to show poodle.
Arrogant "experts" that are under the impression that since something worked on their car it will work the same on every car ever built. It just doesn't happen that way.
People that whine and bring up scoops added to 340 Dusters every.single.time. one pops up. So the economy division didn't add scoops. Everyone knows by now.
I think that's it. Well, probably not.
But on the other hand, I don't let that stuff bother me too much, I just walk by when I see a peeve or just don't comment on it.