Forza Horizon

This one is probably easiest to snag if you attempt to do all the other medal achievements beforehand, so I'll list the ones you'd get through those separately.

Note that you can't use any club cars, they gotta be yours! Also you can sell the cars after getting a challenge, if your budget is tight. I'm trying to keep it DLC free but for convenience sake I'll list those at the bottom.

SIR CHALLENGE-A-LOT ACHIEVEMENT 4/14
It's for doing a challenge in 20 different British cars, take these along for the ride.

o #1 - 2010 Aston Martin One-77 -- from #1 Popularity/1.8 mil value
o #2 - 1958 Aston Martin DBR1 -- Barn Find/6 mil value
o #3 - 1997 McLaren F1GT -- 4 mil value
o #4 - 1956 Jaguar D-Type-- Barn Find/3 mil value

FORD CHAMPION 5/14
13 Fords this time around, one happens to be over a million.

o #5 - 1966 Ford GT40 Mkll -- 1.5 mil value

FERRARI FAN 11/14
Right, this is where it can get difficult. One you'd have to rely on being a lucky fella' and getting the very last Barn Find; The 250 TR. Two, these are very expensive!

o #6 - 1957 Ferrari 250 Testa Rossa -- Barn Find/8 mil value
o #7 - 2010 Ferrari 599XX -- 1.5 mil value
o #8 - 2002 Ferrari Enzo -- 1.2 mil value
o #9 - 1989 Ferrari F40 Competizione -- 1.5 mil value
o #10 - 1996 Ferrari F50 GT -- 1.2 mil value
o #11 - 2005 Ferrari FXX -- 2.5 mil value

NISSAN NINJA 12/14
There's a free sample download of one of the DLC packs that happens to be a relatively cheap Nissan!

o #12 - 1998 Nissan R390 -- Free download/1.2 mil value

REMAINING 13/14
So now you'd need 2 more. I'll still avoid the DLC for now cause there's some relatively cheap supercars(that won't cost 3+ million) that you can score to round it all up!

o #13 - 2012 Hennessey Venom GT -- 1 mil value
o #14 - 2009 Koenigsegg CCX-R Edition -- 1 mil value

ALTERNATIVES AND DLC
If you're any cars short, like you can't trigger the 250 TR or you just happen to have the DLC and the cars are cheap, just replace any of the cars you can't obtain with one of these then!

In Base Game:
o #15 - 2010 SSC Ultimate Aero -- 1 mil value
o #16 - 2010 Pagani Zonda R -- 1.7 mil value
o #17 - 2011 Bugatti Veyron Super Sport -- 2.2 mil value
o #18 - 2008 Maserati MCI 2 Versione Corse -- 1.8 mil value

As DLC:
o #19 - 2012 Pagani Huayra -- 1.8 mil value
o #20 - 2011 Lamborghini Sesto Elemento -- 2.2 mil value/Lamborghini Lover
o #21 - 2012 Ferrari 599XX Evoluzione -- 1.5 mil value
o #22 - 1965 Shelby Cobra 427 S/C -- 1.5 mil value/Snake Charmer


Hope this helped! And check my solution on Forza Legend, it follows the same path just... well, 132 extra cars. D:

You need to earn at least one medal in 14 different cars worth at least 1 million Cr. Press up on the D-pad to see the requirements for the medals.

Beware, although some cars are free to download, they still need to be purchased in game with either in-game credits or real money (MS Points), but that is the case for every car.

Unicorn cars
I do not include "unicorn" cars as free as you need to earn them and they are extremely rare, so most gamers will not have access to them.

Barn discovery cars
Barn discovery cars are available in the main game, but you have to progress through the story and multiplayer, to have them appearing on your map. Then you have to find them in the barn (wrecked). You have to wait until they are fixed before you can use them. There are 9 Barn discovery cars.
* 1964 Aston Martin DB5
* 1958 Aston Martin DBR1
* 1981 BMW M1
* 1992 Bugatti EB110 SS
* 1957 Ferrari 250 Testa Rossa
* 1956 Jaguar D-Type
* 1954 Mercedes 300SL Gullwing Coupe
* 1971 Plymouth Cuda 426 HEMI
* 1965 Shelby Cobra Daytona Coupe

Loyalty cars
To get your loyalty cars you need at least a save file from either FM3 or FM4. Depending on your level, you get those cars:
* 2011 MINI Cooper S (Level 1)
* 2011 Citroen DS3 Racing (Level 5)
* 2012 Dodge Charger SRT8 (Level 10)
* 1969 Chevrolet Camaro SS (Level 15)
* 2008 BMW M3 E92 (Level 20)
* 2012 Jaguar XKR-S (Level 30)
* 2009 Gumpert Apollo S (Level 40)
* 2012 Lamborghini Aventador LP700-4 (Level 50)

Forza Rewards Program
https://rewards.forzamotorsport.net/
Depending on your tier, you get rewards monthly. Redeem them on the site and they will be deliverer in your game within 4 hours. The rewards can be money, cars, tokens,...

Available DLC Packs
* October Car Pack (1957 Chevrolet Bel Air - FREE)
* November Bondurant Car pack (2012 Jeep Wrangler Rubicon - FREE)
* Season pass (2006 Lamborghini Miura Concepts - FREE)
* December IGN Car Pack (1971 AMC Javelin AMX - FREE)
* Rally expansion pack NOT FREE - NO FREE CARS
* January Recaro Car Pack (1995 Ford Mustang Cobra R - FREE)
* Honda Challenge Car Pack - FREE pack, includes 3 free Honda Cars (2013 Civic Si Coupe - 1986 Honda Civic Si - 2013 Honda HDP Fit - FREE)
* February Jalopnik Car Pack (1966 Ford Country Squire - FREE)
* March Meguiar's Car Pack (1998 Nissan R390 - FREE)
* April TopGear Car Pack (2002 BMW M3 GTR - FREE)

Complete List
* 1956 Jaguar D-Type (Barn discovery - main game)
* 1957 Ferrari 250 California (main game)
* 1957 Ferrari 250 Testa Rossa (Barn discovery - main game)
* 1958 Aston Martin DBR1 (Barn discovery - main game)
* 1962 Ferrari 250 GTO (main game)
* 1965 Shelby Cobra Daytona Coupe (Barn discovery - main game)
* 1965 Shelby Cobra 427S/C (DLC)
* 1966 Ford GT40 MkII (main game)
* 1989 Ferrari F40 Competizione (main game)
* 1993 McLaren F1 (DLC)
* 1996 Ferrari F50 GT (main game)
* 1997 McLaren F1 GT (main game)
* 1998 Mercedes-Benz AMG Mercedes CLK GTR (DLC)
* 1998 Nissan R390 (FREE DLC)
* 2002 Ferrari Enzo (main game)
* 2005 Ferrari FXX (main game)
* 2008 Maserati MC12 Versione Corse (main game)
* 2009 Lamborghini Reventón Roadster (main game)
* 2009 Koenigsegg CCX-R Edition (main game)
* 2009 Pagani Zonda Cinque Roadster (DLC)
* 2010 Ferrari 599XX (main game)
* 2010 Aston Martin One-77 (main game)
* 2010 Pagani Zonda R (main game)
* 2010 SSC Ultimate Aero (main game)
* 2011 Veyron Super Sport (main game)
* 2011 Koenigsegg Agera (DLC)
* 2011 Lamborghini Sesto Elemento (DLC)
* 2012 Hennessey Venom GT (main game)
* 2012 Ferrari 599XX Evoluzione (DLC)
* 2012 Pagani Huayra (DLC)
* 2012 Lamborghini Aventador J (DLC)

Summary: 17 cars (main game) + 4 Barn discovery (main game) + 9 cars (non free DLC) + 1 car (free DLC)