US:

Cars I prefer: Nissan X-Terra (National), Taurus (Hertz), Olds Alero (Avis), ANY Toyota, Ford Countour

Cars I hate: ANY BUICK, That new Lincoln LS (why does this luxury car still feel "cheap"), SUV's (other than the X-Terra)


Europe
(This I can give you more info on... As I'm their more often)

Cars to Get: ANY Volkwagen (Sixt rent a Car), Mercedes C/E or S Class (Sixt/Avis/Hertz) ANY BMW (Sixt Rent a Car/AVIS/Hertz). Vauxhall/Opel Vectra, Ford Mondeo 1.8 or 2.0 (Hertz), Saab 95 (Avis), Ford Focus (All), Peugeot 206, 306 or 406 (Hertz and others), Volvo C or S Series

Cars that are mediocre: (If nothing else is available); Fiat Marea, Vauxhall Astra, Chyrsler Neon,

Cars to AVOID at ALL costs (my 2 cents): Toyota Avensis (has some funky gearbox problem won't alway shift into 1st - had this happen on 3 CARS - 3 different times), Vauhall/Opel Zafira, Mercedes A-Class

I rent at least 4 times a month in Europe, so if anyone (US based) has any specific questions on renting their and getting a descent car in the group you booked, let me know. I think over the last 5 years I've rented nearly everything.