![Image](http://upload.wikimedia.org/wikipedia/commons/thumb/a/a9/1955_Mercedes-Benz_300SL_Gullwing_Coupe_34.jpg/800px-1955_Mercedes-Benz_300SL_Gullwing_Coupe_34.jpg)
And they weren't used in Mercs until recently (2010 Merc SLS).
![Image](http://upload.wikimedia.org/wikipedia/commons/thumb/2/2e/Mercedes-Benz_SLS_AMG_%28C_197%29_%E2%80%93_Frontansicht_ge%C3%B6ffnet%2C_10._August_2011%2C_D%C3%BCsseldorf.jpg/800px-Mercedes-Benz_SLS_AMG_%28C_197%29_%E2%80%93_Frontansicht_ge%C3%B6ffnet%2C_10._August_2011%2C_D%C3%BCsseldorf.jpg)
But during those 60 years they were used by some other -bizarre- cars:
Production cars
Autozam AZ-1 (Suzuki Cara)
Bricklin SV-1
Bristol Fighter
DeLorean DMC-12
De Tomaso Mangusta (engine compartment)
Gumpert Apollo
Hofstetter Turbo
Isdera Commendatore 112i
Melkus RS 1000
Melkus RS 2000
Mercedes-Benz 300SL
Mercedes-Benz SLS AMG
Pagani Huayra
(NSU) Thurner RS
Tesla Model X
Quant E
Quant F
And kit cars
AMT Piranha
Bradley GTII
Dare DZ
Eagle SS Mk1
Elite Enterprises Laser 917, inspired by the Porsche 917
Fiberfab Aztec 7, a loose replica of the Alfa Romeo Carabo concept car (which has scissor doors).
Fiberfab Caribee/Banshee
Innes Lee Scorpion K19
Pelland Sports
Replicar Cursor
RPB GT
Burton Car Company hardtop
Siva S160 Spyder
http://en.wikipedia.org/wiki/Gull-wing_door
Compare this to Scissor doors (Lambo doors)
First used in a production car in the Lamborghini Countach in 1974
![Image](http://upload.wikimedia.org/wikipedia/commons/7/74/Countach_Scherentueren.jpg)
And then continuously used in the Diablo, Reventon and Aventador.
http://en.wikipedia.org/wiki/Scissor_doors
Since Lamborghini has continuously used scissor doors for the last 41 years, they had become their trademark.
So Spyker and Koenigsegg just look as copycats. Even though the later has a different door mechanism, that just looks Lambo-door to the non-nerd.
By some reason butterfly doors just don't look as good as Gullwing or Lambo doors
http://en.wikipedia.org/wiki/Butterfly_doors
Some of them still look quite Lambo-doors copycats to the casual observer
SSC Aero
![Image](http://upload.wikimedia.org/wikipedia/commons/thumb/8/80/SSC_Ultimate_Aero_TT_-_1.jpg/800px-SSC_Ultimate_Aero_TT_-_1.jpg)
Sliding doors hold promise, specially if automated (with an electric motor)
But I suspect they will rattle quite badly, just as those on minivans do.
![Image](http://upload.wikimedia.org/wikipedia/commons/thumb/e/ec/BMWZ1.jpg/800px-BMWZ1.jpg)
http://en.wikipedia.org/wiki/Sliding_door_(vehicle)