Assuming we aren't limiting ourselves to the current ranges of these manufacturers....
AC: 427 Cobra
Alfa Romeo: Series 1 Alfasud
Aston Martin: DB9
Audi: umm.....if I really must choose an Audi, RS6
Austin: Clifton Heavy 12/4 (Gumdrop!)
Bentley: T2
BMW: again....if I must, E61 M5 Touring
Bugatti: Type 35
Buick: Grand National/GNX
Cadillac: '59 Miller-Meteor ambulance conversion
Chevrolet: Corvette ZR-1
Chrysler: Newport
Citroen: DS
Dodge: '69 Charger R/T Hemi
Ferrari: 365GT4 2+2
Fiat: Abarth 695SS
Ford: Escort Cosworth
Honda: NSX
Jaguar: Series 1 E-Type
Jensen: Interceptor
Lamborghini: Miura SV
Lexus: ugh....nope, cant even bring myself to think about it
Lotus: original Elan
Mazda: MX-5 (just so I could stuff a GM LS small-block V8 in it to create a neo-Cobra)
Mercedes: 300SL Gullwing
Mitsubishi: Lancer Evo III
Nissan: 240Z
Oldsmobile: Vista Cruiser
Peugeot: 607, never been a fan of Peugeots but the 607 should be just about big enough not to be un-neccessarily cramped
Plymouth: '70 Roadrunner Hemi
Pontiac: last gen Trans Am
Porsche: 911S, before the wheelbase was lengthened
Renault: 5 Turbo
Rolls-Royce: Silver Shadow
Rover: P5B
Seat: 600, since it's mostly Fiat and therefore half decent
Skoda: Felicia
Subaru: Legacy
Toyota: Aygo
TVR: Tuscan mk2
Vauxhall: VXR8 Bathurst
Volkswagen: '67 1500 Beetle
Volvo: 240
***edit***
Added several American manufacturers, plus Volvo.
***edit 2***
A few more added.