The worst idea that has been comitted to steel are:

Pimpmobiles:

http://youtu.be/def4tAQe9aA 

Donks. Most of the criticism is racist, but there are legitimate artistic and technical reasons to be critical of them.

http://youtu.be/2fLEtuXKiyw

70's era customs:

http://youtu.be/MdEH2qP5oUk

Who needs these jacked up rear ends, chromed Jag axles, Wolfrace wheels, murals? This brings us onto Custom Vans:

http://youtu.be/Ue-S3sKQQPs

Rolling shag palaces that defy taste. If I had one, I'd do it up as a salt flats style push truck. VW's are the exception to the rule.

Boy Racer cars:

http://youtu.be/VKCXh7o0DqQ

They look like they will tip over at any time and handle badly. They show themselves up for what they are on the track. Like the boy racers, they're people with no taste or sense of appropriateness. If you drag race, you put on Minilites.

 

Thee Shake Spears said:

"Rice Rocket" racers!  The ones with exhaust pipes that have 8 inch diameters!!  Fuckin HATE those things!!!!  They go up & down our street at all times of the night...WHIIIIIIIIIIIIIIIEEEEE!!!!!!!"....GAWT DAMN KIDS!!!! XD Sounds like a damn go kart!

The DONKS are rediculous.  I saw one when I lived in Atlanta (or the ATL if you prefer) that was "Cool Whip" themed with an empty bucket of whip dangling from the back bumper.

I also hate truck nuts...I don't want to look at any nuts- fake or real.

"Rice Rocket" racers!  The ones with exhaust pipes that have 8 inch diameters!!  Fuckin HATE those things!!!!  They go up & down our street at all times of the night...WHIIIIIIIIIIIIIIIEEEEE!!!!!!!"....GAWT DAMN KIDS!!!! XD Sounds like a damn go kart!

I am an admitted car snob, but I am no fan of "art cars".  I include "theme cars and bikes" and Ratrods in that same subheading. Anything built for shock value is only going to be topical for a small period of time. I try my damnedest to build timeless and well thought out cars and bikes.