Ok, here's my FULL list (this only includes things that I have had SOME chance of ever seeing so far). Yeah, that's right, I put them in alphabetical order.

Aston Martin DB4
Aston Martin DB6
Aston Martin One-77
Aston Martin V12 Zagato (or any Zagato anything for that matter)
Audi R8 GT
Bugatti EB110
Bugatti Veyron Vitesse
Ferrari 250 GTO (I think the one I saw was a replica)
Ferrari 288 GTO
Ferrari 512BB
Ferrari FXX
Ferrari LaFerrari
Ferrari P4/5
Gumpert Apollo
Hennessey Venom GT
Any Koenigsegg besides a CCX at a dealer
Lamborghini Diablo SV
Lamborghini Gallardo Squadra Corse
Lamborghini Sesto Elemento
Lamborghini Reventon
Lamborghini Veneno
Laraki Epitome
Maserati MC12
McLaren F1
Mercedes CLK GTR
Mercedes SLR McLaren Stirling Moss
Mercedes SLS AMG Black Series
Mosler MT900
Morgan Aero 8
Noble M12 GTO 3R
Any Pagani Zonda
Porsche 911 Speedster
Any Ruf besides CTR2 at a show (might see a CTR3 soon though)
Saleen S7
Any Spyker besides C8 Spyder at a dealer

Seen, but no legit spots:
Bentley Brooklands Coupe
Bugatti Veyron Grand Sport
Dodge Viper ACR
Ferrari 360 Challenge Stradale
Ferrari 456
Ferrari Daytona
Ferrari F40
Jaguar XJ220
Lamborghini 400GT
Lamborghini Aventador Roadster
Lamborghini Espada
Lamborghini Gallardo Super Trofeo Stradale
Lexus LFA (have spotted a Nurburgring)
McLaren P1
Mercedes CLK DTM
Mercedes SLR McLaren
Noble M400
Porsche 918 Spyder
Rossion Q1

Probably forgetting a lot.

I've seen it all but never a Veyron. It really bugs me

I still haven't seen a McLaren F1 or a Veyron.

I see what you did there :)

Hahaha

I've never seen a Lykan Hypersport.

I've never seen a Ssangyong...
Or:
Lada
Moskivitch
Yamal
JAC
Lieger
Peugeot 5008
Dongfeng
GAZ
UAZ
Troller
Agrale
Opel
Vauxhall
Holden
Ford Ka
Mercedes Benz V Class
Mercedes Benz A Class
Proton Satria Neo
Mitsuoka Galue (I have seen a Viewt though)
New London Taxi
Dacia
Smart Forfour
The list will continue...

Ya all those except i've seen an opel GT and an older holden monaro

still havent seen an aventador on the road
Veyron
this i a rather large list, so im not gonna write it all out

I interpret this to mean cars you've never seen "in the wild" but seen at events/dealers, so here's my list:

Bugatti Veyron
McLaren P1
McLaren 650S
Porsche 918 Spyder
Porsche 959
Ferrari F50
Ferrari 456
Ferrari 599
Ferrari FF
Aston Martin V12 Zagato
Aston Martin DB AR1
Mercedes SLR McLaren
Lamborghini Countach
Maserati MC12 Corsa
Maserati Birdcage
Rossion Q1
Panoz Esparante

If it means cars you've never seen, here's a few:

Ferrari LaFerrari
Ferrari 288 GTO
Ferrari 308 GT4 Dino
Any Pagani
Any Koenigsegg
Any Noble

i am not going to bug anybody with my list because it is longer than u can comphrehend
ive never even seen a db9
no hypercars

Alfa Romeo 8C
Ferrari 458 Speciale A
Lamborghini Aventador SV
Ferrari F50
Ferrari SA Aperta
Any Koenigsegg
Spyker C8 Aileron
Jaguar XJ220
Bugatti EB110
Mercedes SLS AMG Final
Mercedes-Maybach S600
Bentley Continental GT3-R
Mercedes SLR McLaren

Due to car shows there isn't a lot I haven't seen, in the wild though, still haven't seen a lot. So here's some I have seen at shows but not on the road.
Ferrari Enzo
Ferrari F50
Ferrari 458 Speciale Aperta
Ferrari LaFerrari
Pagani Huarya
Porsche 918
Koenigsegg One:1
Gumpert Apollo
Lexus LFA
Any Ultima
Standard Supra
Lamborghini Countach (real one)
Ferrari Daytona
Shelby Cobra (all replicas like Dax spotted)
Noble M400
Hardtop E-type
Porsche 959
Jaguar XKRS-GT
Ferrari 250 GTO
599 GTO

I haven't seen any car that costs over $800,000. Other cars I have not seen are:
599 GTO
650S
Shelby Cobra (a real one)
All classic super cars except for the Ferrari 246 Dino and the Jaguar E-type
I've probably missed a few, but that's my list.

p1
laferrari
bugatti
pagani
koenigsegg
veneno