Mine
1. All time favorite is Duesenberg, probably the best built cars ever on the planet, or the best that ever will be. A time, place, and experience that will likely never be duplicated. They were simultaneously the best built, the fastest, the most luxurious, and the most expensive cars on the planet at the time, and there was nothing that even approached their supremacy, no comparison within even shooting distance. Premium product in short supply.
2. Cadillac - The expression "It's the Cadillac of...." does not mean it's the nicest, though they were luxury cars of their time. Cadillac was the first car company to use standardized, interchangeable parts. So to say "It's the Cadillac" means it's the standard. For the first time you could take parts off of one car and put onto another one, and it would fit every time. Their V8 would become an industry wide standard of quality, way ahead of everyone else. This was largely not the case on the rest of the auto industry in the early years.
3. Ferrari - Passion for racing and a willingness to put race bred technology on the street. I believe there is no other proper car maker in the world that even comes close to Ferrari's vision and boldness to realize it. Number one in the world today, hands down. Enzo Ferrari was legendary for his indifference to customers, that's why we now have Lamborghini, but his passion alone produced street going cars with world class racing potential. The 250 GTO SWB will likely never be equaled in contemporary capability, it was an astounding, world-beating car that rolled out of a small factory with a dictatorial and super-focused owner. Why do you think Fiat bought them after that?? (Interesting historical note. Enzo Ferrari's extensive use of 12 cylinder engines came from his early encounter with a 12 cylinder Packard army car, Packard made the first 12 cylinder. Ferrari later said he married the twelve cylinder and never divorced it.)
4. The original Dodge - John and Horace Dodge were the genius engineers that actually made the original assembly line for Henry Ford, (the original building still exists in Detroit, and is not a museum, just an old non-descript building.) And the truth is, they actually engineered and manufactured the chassis, engine, and transmission of original Ford cars and for several years until Ford could start making his own, which were not as high in quality as they Dodge made 'rigs' as they were called. They had a huge parts business selling parts for many types of cars and had a tremendous reputation. When they decided to build their own car to occupy the niche between Ford and the more expensive cars (their target was around $800, which was alot at the time), 22,000 dealership applications arrived before they had even finished the car. Both brothers died within six months of each other from the Flu, and John's widow built a 180,000 sq. ft. Tudor mansion in Pontiac, MI, that still stands today. I love these guys because of their vision. I also love the 60's and 70's era Mopar cars, the essence of the muscle cars. All the other folks postured and talked tough, but Mopar owned the muscle car era without qualification.
5. Fiat - I like these cars strictly by accident and only because I happen to have owned them for just over 10 years. The Italians are idiosyncratic in almost every conceivable expression of humanity, from art to wine to cars. Most people either love it or they hate it. I love it. Fiats are not the epitome of anything, but most closely resemble the GM of Europe, and they've always made good consumer cars. If you take the X1/9 to be typical of Fiat, you'd be wrong. The X is a unique car from a unique era, notice how Fiat hasn't done anything close to that since. Their 8V from the 50's was an incredible car, but Fiat is the mass producer of cars in Europe as much as any other and overall, just a mass produced car. The Spider and X are bright spots and hence have a cult following. I like Fiat for what it is, there is nothing otherwise overwhelmningly impressive about them as a car maker. Incidentally, Packard was founded the same year as Fiat, 1899. It's noteworthy too that Packard first used a steering wheel instead of a tiller!