List the cars you own in Forza.
FM4:
Veyron Super Sport
Saab 9-3 Turbo X
Q7 V12 TDI
BMW M5
SL65 AMG Black Series
AM DBS
F430
Ferrari FF
599 GTO
458 Italia
MP4-12C
SLR Stirling Moss
Aventador
R8 V10
One-77
458 Italia (with enzo V12)
Gallardo Superleggera
LP670
Sesto Elemento
Aventador
#83 Risi Competizione F430GT
Gallardo Superleggera
LP670
Koenigsegg Agera
458 Challenge
F430 (Mario edition)
Aventador
Reventon
599GTO
Veyron 16.4
F430
#12 Nissan GTR
Pagani Zonda R
#007 AM DBR9
Bentley Speed 8
#10 Peugeot 908

Meh. I'm not that good on 4 but Horizon is awesome. List later.

Its the opposite with me. I have like 20 cars on horizon including the barn finds, but all my cars are fully upgraded.

It isn't that good but I don't care.

1989 Toyota MR2 SC - E 274
1971 Lotus Elan Sprint - E 274
1988 Mitsubishi Starion ESI-R - D 349
1960 Chevrolet Corvette - D 349
1970 Chevrolet Chevelle SS-454 - D 350
2011 Cïtröen DS3 - D 350
1982 Lancia O37 Stradale - C 425
2008 Land Rover Range Rover Supercharged - C 425
2000 Honda Integra Type-R - C 425
1967 Chevrolet Corvette Stingray 427 - C 425
2010 Peugeot RCZ - C 425
1990 Mercedes-Benz 190E 2.5-16 Evolution II - C 425
2008 Mitsubishi Lancer Evolution X GSR - B 499
1992 Honda NSX-R - B 500
2005 Lotus Elise 111S - B 500
2013 Ford Focus ST - B 500
1967 Lamborghini Miura P400 - B 500
2010 Ford Shelby GT500 - B 500
2011 Ford Ka - A 561
2009 Ford Fiesta Zetec S - A 598
1971 Ford Mustang Mach 1 - A 599
2010 Mercedes-Benz C63 AMG - A 599
2010 Chevrolet Corvette Grand Sport - A 600
2010 Mercedes-Benz E 63 AMG - A 600
1970 Ford Mustang Boss 429 - A 600
2010 Ferrari 458 Italia - R2 853

That was 4, Not Horizon.

Updated :

Actually, I think it is :/

1989 Toyota MR2 SC - E 274
1971 Lotus Elan Sprint - E 274
1970 Ford Mustang Boss 429 - D 349
1988 Mitsubishi Starion ESI-R - D 349
1960 Chevrolet Corvette - D 349
1970 Chevrolet Chevelle SS-454 - D 350
2011 Citroen DS3 - D 350
1982 Lancia 037 Stradale - C 425
2008 Land Rover Range Rover Supercharged - C 425
2000 Honda Integra Type-R - C 425
1967 Chevrolet Corvette Stingray 427 - C 425
2010 Peugeot RCZ - C 425
2008 Mitsubishi Lancer Evolution X GSR - B 499
2005 Lotus Elise 111S - B 500
2013 Ford Focus ST - B 500
1967 Lamborghini Miura P400 - B 500
2010 Ford Shelby GT500 - B 500
2011 Ford Ka - A 561
2008 Aston Martin DBS - A 598
2009 Ford Fiesta Zetec S - A 598
1971 Ford Mustang Mach 1 - A 599
2010 Spyker C8 Laviolette LM85 - A 600
2010 Chevrolet Corvette Grand Sport - A 600
2010 Mercedes-Benz E 63 AMG - A 600
1970 Ford Mustang Boss 429 - A 600
2009 Mercedes-Benz SL 65 AMG Black Series - A 600
1967 Ferrari 330 P4 - A 600
2008 Dodge Viper SRT10 ACR - S 698
2009 Mercedes-Benz SLR Stirling Moss - S 699
2011 Ferrari 599 GTO - S 699
2010 Ferrari 458 Italia - S 700
1999 Ferrari 360 Modena - S 700
1993 McLaren F1 - S 700
2011 McLaren MP4-12C - S 700
1988 Lamborghini Countach LP5000 QV - S 700
2010 Bertone Mantide - S 700

1ST HALF

1992 Volkswagen Golf GTi 16v Mk2 - R3 734
1992 Honda NSX-R - R3 747
2010 Mercedes-Benz C63 AMG - R3 762
1990 Mercedes-Benz 190E 2.5-16 Evolution II - R3 784
2009 Pagani Zonda Cinque Roadster - R3 798
1998 Mercedes-Benz AMG Mercedes CLK GTR - R3 798
2011 Chevrolet #04 Chevrolet Racing Monte Carlo SS Stock Car - R3 800
2009 Bugatti Veyron 16.4 - R3 800
2011 Lamborghini #08 West Yokohama Gallardo LP560-4 - R3 800
2011 Holden #11 Pepsi Max Crew Commodore VE - R3 800
2004 Ferrari F430 - R2 862
2008 Mazda Furai - R2 875
2005 Honda #18 TAKATA DOME NSX - R2 875
1997 McLaren #43 Team BMW McLaren F1 GTR - R2 875
2008 Mercedes-Benz Mercedes-AMG C-Class Touring Car - R2 875
2006 Aston Martin #007 Aston Martin Racing DBR9 - R2 875
2008 Acura #15 Lowe's Fernandez ARX-01b - R1 998
2003 Bentley #7 Team Bentley Speed 8 - X 999
2011 Peugeot #10 Matmut-Oreca 908

Also, I've got 2,082,673 credits but I'm not sure what to spend it on.

Horizon list later

2012 Honda HPD Fit - E 199
1954 Mercedes-Benz 300SL Gullwing Coupe - D 247 - Grey
1964 Aston Martin DB5 - C 315 - Grey
2011 MINI Cooper S - C 342 - Red
1971 Plymouth Cuda 426 HEMI - C 352 - Blue/Black
1957 Ferrari 250 Testa Rossa - C 364 - White
2011 Citroen DS3 Racing - C 388 - Black/Orange
1970 Ford Mustang Boss 429 - C 400 - Orange
1956 Jaguar D-Type - B 409 - Grey
2010 Maserati GranTurismo S - B 491 - Matte Dark Blue
2011 Ford F-150 SVT Raptor - B 494 - White/Green/Brown
2012 Dodge Charger SRT8 - B 495 - Black
2011 BMW 1 Series M Coupe - B 499 - White
2011 Subaru WRX STI - B 500 - White/Black/Gold
2011 MINI Cooper S - B 500 - Yellow/Black
2012 Dodge Challenger SRT8 392 - A 507 - Black/Yellow
1965 Shelby Cobra Daytona Coupe - A 529 - Blue/White
1988 Lamborghini Countach LP5000 QV - A 537 - White
2009 Ferrari California - A 539 - White/InsanelyWeirdMixtureOfColours
2005 Honda NSX-R GT - A 541 - White
1991 Ferrari 512 TR - A 542 - Yellow
2011 Lotus Evora S - A 546 - Green/Black
1995 Ferrari F355 Challenge - A 553 - Metallic Yellow
2002 BMW M3 GTR - A 565 (Soon getting tuned) - 2005 NFSMW Design
2012 Chevrolet Camaro ZL1 - A 578 - Yellow/Black
1966 Ford GT40 MkII - A 582 - Black/Yellow
2005 Ford GT - A 593 - Gulf Design
2012 Aston Martin Vanquish - A 599 - White
2013 Scion FR-S - A 599 - Black/White
2012 Bentley Continental GT - A 600 - Blue
1997 Lamborghini Diablo SV - A 600 - Light Blue
1991 BMW M3 - A 600 - Black
1997 Mazda RX-7 - A 600 (Soon undergoing more upgrades) - White/Black
2002 Honda Integra Type-R - A 600 - Black/Red
2003 Ferrari 360 Challenge Stradale - S 623 - Red/Italian Stripe
1987 Ferrari F40 - S 632 - Matte Blue
1965 MINI Cooper S - S 638 - Fantasy Police Design
2011 Audi R8 GT - S 648 - Metallic Yellow
2010 Lexus LFA - S 653 - Lime Green (Soon Changing Colour)
2011 Ferrari 458 Spider - S 653 - Green
1987 RUF CTR Yellowbird - S 655 - Black

2012 Ferrari F12berlinetta - S 667 - Green
2013 Viper GTS - S 681 - White/Red/Grey
1958 Aston Martin DBR1 - S 681 - Dark Green
2011 Ford Transit SuperSportVan - S 692 - British Police
1992 Volkswagen Golf GTi 16v Mk2 - S 694 - Black/Green
1995 Volkswagen Corrado VR6 - S 694 - White
2004 Mitsubishi Lancer Evolution VIII MR - S 700 - GreyMonster Energy Decals
2010 Lamborghini Murcielago LP 670-4 SV - S 700 - Yellow
2006 Lotus Exige Cup 240 - S 700 - Lime Green
1994 Mazda MX-5 Miata - R3 736 - Drifting Design
2004 Saleen S7 - R3 754 - Blue/Black
2012 BMW M5 - R3 777 - Dark Blue
1999 Mitsubishi Lancer Evolution VI GSR - R3 786 - Rally Design
2011 RUF RGT-8 - R3 788 - White/Red 911 GT3 RS Design
1998 Toyota Supra RZ - R3 792 - Yellow/Black
2010 Viper SRT10 ACR-X - R3 800 - Black/White
1983 Audi Sport quattro - R2 804 - Red
2013 Ford Shelby GT500 - R2 822 - Blue
1981 BMW M1 - R2 853 - Orange
2008 Mitsubishi Lancer Evolution X GSR - R2 878 - Matte Black
2012 Lamborghini Aventador LP700-4 - R2 882 Yellow (NorthUK00 gifted me:) )
2006 Audi RS 4 - R2 900 - Race Design
2010 Aston Martin One-77 - R2 900 - Baby Blue
2010 BMW M3 GTS - R1 908 - Orange
2010 Saleen S5S Raptor - R1 908 - Yellow
2002 Nissan Skyline GT-R V-spec II - R1 926 - Black/White
2013 Viper GTS - R1 936 - Dark Blue
2011 Lamborghini Gallardo Superleggera - R1 939 - Matte Lime Green
2010 Ferrari 599XX - R1 940 - Yellow
2012 Hennessey Venom GT - R1 953 - Baby Blue
2012 Lamborghini Aventador LP700-4 - R1 956 - White
2012 Lamborghini Aventador J - R1 959 - Matte Grey
1992 Bugatti EB110 SS - R1 967 - Blue (275mph!)
2012 Nissan GT-R Black Edition - R1 968 - Green/Purple
2012 Gumpert Apollo Enraged - R1 978 - Chrome Green
2009 Koenigsegg CCX-R - R1 982 - Black
1996 Ferrari F50 GT - R1 987 - Red
2011 Bugatti Veyron Super Sport - R1 989 -Black/Blue
2011 Radical SR8 RX - R1 989 - Pepsi Max Design
2012 Ultima GTR - R1 998 - Matte White

Veyron GranSport
Nissan GTR R35
Nissan Skyline R34
Dodge Viper GTS
Dodge Viper ACR
BMW M6
BMW M3
BMW M5
Cadillac Escalade ESV
Ford Transit
Ford GT
Ford GT500
Ford RS2000
Ford Focus ST
Chevy Camaro ZL1
Chevy Corvette ZR1
Dodge Charger SRT8
Saleen S7
Saleen S5S Raptor
BMW M1
Bugatti EB110
(....all barnfinds)
Audi R8 GT
Audi RS4
Audi TTRS
Bentley Continental
Lotus Evora
Audi Sport Quattro
Toyota GT86
Toyota Supra Turbo
Lamborghini Murcielago SV
Lamborghini Diablo
Lamborghini Gallardo Superleggera
Lamborghini Aventador
Ferrari 458 Italia Spider
Ferrari FF
Ferrari California
Maserati GranTurismo
Hennessey Venom
Koenigsegg CCX
Radical SR8
Mercedes SLS AMG
Mercedes C63 AMG
Mercedes SL65 Black
Mercedes S65 AMG
Subaru Impreza WRX STI
Ford Focus RS
Lexus LFA
Lexus IS-F
Mini Cooper S
Ford Raptor
Ferrari F40

Ughhh i'll list mine later there are sooooooo many

I haven't played forza for ages but from memory:

FM4
zonda c12
zonda cinque roadster
Zonda R
Sesto elemento
all 4 McLaren f1s (gt and racers)
Mp412-c
Furai
Mantide
Spada
Enzo
333sp
330p4
250 California
F40 c
F50
Apollo
Diablo gt
Murcialago
Cc8s
Ccxr
Ccgt
Eb110ss
One 77
dbs
Spyker c8 lm86
r8 lms
Both calsonic skylines
R34 gtr
Tuscan
Sagaris
Speed 12
Audi R15
288 gto
Audi r8 (lemans)
BMW m3 art car
dbr9 (gulf one)
Lfa
Gt40 mk2 (some idiot put a buyout of 12000 on it :D)
BMW v12 lms
Saleen raptor
Charger daytona
Countach
And a few hatchbacks and muscle cars.

I can imagine i missed a few too as that's all from memory

How the hell are you able to afford that?

Luck on the auction house, when fm4 first came out I overplayed it got bored and spent hours on the auction house waiting for idiots to put cars up for really cheap, I got a sesto elemento for 600k buy it now, a clk gtr for 30k (that I then resold for 400k), and so on