Just a note on some of my personal favorites:
FIAT / ALFA ROMEO - why? Sure, make all the "Fix it again, Tony" jokes you want. Fact is, Fiat is still one of the largest automakers on the planet, and they have revamped sufficiently to buy 37% or so of Chrysler. Alfa Romeo simply outdoes everyone in terms of design.
FERRARI - for the F1 racing, of course! I am a huge Schumacher fan (and apologist, for his last season), and love the 1-2 punch of Raikkonen and Massa. Just goes to show that Ferrari has the best all around team when Kimi can win one year, then him and Massa can nearly pull out the constructor's AND a driver's championship the next year when working together. Ferrari has two great cars in every race, and I don't see anyone beating them in the constructor's any time soon.
MERCEDES-BENZ - I own an E-class (2002 E320 4Matic) and don't plan on straying any time soon. There's so much to love about these vehicles, I don't even know where to start. Extremely smooth, well handling, yet one still feels connected to the road when driving a Benz.
LAND ROVER - if I were to get an SUV, it would be a Land Rover LR3, HSE. Beautiful vehicle if you need to offroad.
BMW - if I could get a new car today - at any price - it would probably be an M5 sedan (still good to use as a family car, but sport-oriented for really fun driving). I've driven a few BMWs and have loved all of them, but I'm more a 5-series guy than a 3-series guy. For a more "tame" vehicle, I'd love a 535xi wagon.
HONDA - I still have a softspot for the lovable "second best to Toyota" (in sales, NOT quality of vehicles - IMHO). For nearly ten years I drove nothing but Hondas, then switched to Benz and well...how can you go back? I still keep an eye on all things Honda/Acura from time to time, but I'm not really impressed with Acura's sedan lineup lately. I like the newer SUVs, but that grille has got to go.
You'll notice an absence of American cars here. That doesn't mean I hate American vehicles; it just means I'm more impressed - at the moment - with foreign offerings. Calls to place damaging tariffs on foreign vehicles will only hinder innovation; Cadillac and Ford, at least, have proven in recent years that they can keep up with foreign cars if they put their minds to it.
Vehicles I have owned over the past ten years or so:
1996 Honda Accord 25th Anniversary Edition (4-cyl) - sold
2003 Honda Accord EX-L (4-cyl) - sold
2006 Honda Accord EX-V6 - sold
(to interject: I was an upgrade hog for a while, as you can see)
2000 Mercedes-Benz E430 4Matic (totaled December 2006)
2002 Mercedes-Benz E320 4Matic (current)
My wife owned a 2002 VW Passat - more on that story later - and currently drives a 2000 Lexus ES300.