I know for a fact that this is highly illegal, possibly a felony for imitating an emergency vehicle or something like that, I've seen a couple BMWs with RGB halos that they leave in gay pride mode, flashing all sorts of colors to distract oncoming drivers.
Short of that, I've seen the stupidest cars with halos and LED borders. It looks cool on a modern looking, higher end car. On a $15k Kia or 2003 F150 it looks like total trash.
It's not technically lighting itself, but full blacked tail lights are possibly the worst mod I can think of for a vehicle. It makes you look like some 14 year old kid who goes home and plays Call of Duty on XBOX while drinking mountain dew, as well as being a huge hazard for cars behind you at night. Blacked out is just distasteful all around, on any component.