I have heard it said that accessorising vehicles dates back to Roman times when young gladiators would personalise their chariots, both aesthetically and functionally.
From what I have found, I believe that by 1950 the car had become only secondary to the customisations.
Mobil crest key, Fins for the rear fender line, Trouble light
The Buick also boasted Child Safety locks and adjustable steering, even if it was a workshop job to adjust both of these.
Other Buick options and Buick Engineer Approved Accessories.
Indicators
Windshield washers
Fog lights
Tinted glass (Eze Eye Glass in the Roadmasters)
Signal seeking radio with a foot switch for the driver to change the station
Auto windows and seat adjustment (Standard on the Roadmasters)
Heaters and window demist.
Automatic lights in the cabin, boot/trunk and glove box.
Fender Skirts
Polaroid Glare Shield
Wheel Trim Rings
Fire Extinguisher
Sun Visor for split and full windshields
Non Buick Options
E-Z Dim'r Dimmer switch pedal. Fitted over the dimmer button on the floor to make it easier to locate the dimmer. This would become the third pedal on a Super or Roadmaster. Add the same to the radio seek button on the floor and you have four pedals to play with. I have done this on my car and it makes the floor look like a pipe organ.
This is without a doubt the ugliest option for a 1950Buick. It is added to cover the central tooth. The instruction sheet boasts that fitting this will protect the central tooth from scratches or dents while parking close to a wall. I wonder if there is something that you can put over this item to protect it?
Bug deflectors 
Signal Booster for the radio antenna
Hat holder
Coat Hook
Pen Clip
Altimeter with Parking ticket clip
Steering column mounted document wallet
Swamp Coolers
Vacuum operated fan
Vacuum cigarette lighter