Anything that detracts from the car and its design. A display of general aesthetic ignorance.
Body kits that ignore all the lines and design motifs of the car. Sometimes unpainted, or painted different colours.
Fake body kit vents and stick on port holes. I recently saw a Z3 whose owner had stuck buick port holes above the vents. Unbelievable.
Paint jobs or wraps that work against or obscure the shapes and lines of the car.
TRD stickers.
Carbon fiber glued over original parts.
Stickers to denote what upgrades you have. Who gives a s*it about what kind of brake pedals you've installed?
Misappropriated badges and emblems, often meant for other cars. Type R Toyotas. Porsche Turbo badges on a BMW.
Farty 4" exhaust tips on cars pushing out less than 130hp.
Rubberised steering wheel covers in random colours.
Blue LEDs on windshield washer jets.
Ornately shaped license plate frames - chains, blades, barbed wire.
Bits of random chrome trim accent.
General busyness and hodge podginess.
Platinum motor sports.
It's all subjective though, isn't it.