Cars That Are So Rare Only One Of Them Exists

In the supercar and hypercar world, it's very difficult to stand out. A regular Ferrari, Lamborghini, or McLaren won't cut it for the most discerning collectors, who will already own a garage full of similar cars. These collectors desire something even rarer, specifically, something that no one else is lucky enough to own. To find that one-of-a-kind crown jewel for their collection, they have two options: either try to get their hands on a one-off creation like a concept car or prototype — or convince a manufacturer to build them their own unique creation that's exactly to their tastes.

Often, these one-off specials are incredibly expensive to purchase, costing their owners millions of dollars, but they're arguably all worth their asking price. After all, many collectors prioritize exclusivity over all else, and it doesn't get much more exclusive than having a car that no one else on the planet has the privilege of owning.

Of course, not every one-off is sold to a private collector. Manufacturers often keep their concepts, prototypes, and testing vehicles within their own collections, sometimes exhibiting them at museums, but more often than not, hiding them away in storage where only a handful of employees are allowed to view them. Whether they're hidden away in a collector's garage or in a manufacturer's storage facility, these cars are all so rare that most of us will probably never get to see them in the flesh.

Unveiled in 2010, the Pagani Zonda Uno was supposed to be a final send-off for the Zonda model. It was commissioned by a member of the Qatari Royal family, who also owns a large collection of other cars in the same shade of turquoise blue, according to Motor1. The Zonda Uno used the same AMG-sourced 7.3L V12 engine present in the "regular" Zonda, which was capable of sending 690 horsepower to the rear wheels. The Uno's unique bodywork was reportedly inspired by the Zonda Cinque and the track-only Zonda R, which themselves were both incredibly rare, with only 10 units and 16 units produced, respectively.

The Qatari Royal family quickly got bored with their new toy, listing it for sale just a year after they were handed the keys, according to Car News China. The Uno was then bought by a Chinese businessman and shipped to Shanghai, where it's believed to still reside today.

The BMW Z18 was an off-road convertible concept that was technically the brand's first 4x4, pre-dating the X5 by about four years. It was essentially a Z3 roadster with a lift kit and all-wheel drive, plus a waterproof interior that could be hosed out after a long day on the trails. The company claimed the Z18 could also cross "flat stretches of water," although it didn't specify how deep. The design was created by the company's Technik division, which was a small team of designers and engineers that were separated out from the main company to work on pioneering designs like this one.

Suffice it to say, the Z18 was deemed too niche to ever be considered for production, but parts of its design did actually make it to dealerships in the form of the X5. The biggest element that was carried over to the production X5 was the concept's V8 engine, which made 355 horsepower according to Motor1. The idea of a convertible SUV has been occasionally revisited by other manufacturers like Nissan and Land Rover — but without much commercial success. It seems that BMW made the right call leaving the Z18 as a one-off that was eventually forgotten about by all but the brand's most dedicated fans.

Zagato and Alfa Romeo have a relationship that goes back decades, with the design studio being responsible for many of the brand's most iconic racing cars in the Sixties. Two of those race cars were the TZ1 and TZ2, and both were bought up by a German collector and superfan of the brand, Martin Kapp. In the late 2000s, he commissioned Zagato to make a successor to the two classics, with the resulting TZ3 debuting at the Concorso d'Eleganza Villa d'Este in 2010, according to Top Gear.

Both of the original Sixties racing cars used aluminum tubular frames, but to keep weight to a minimum, the TZ3 was built with a carbon-fiber monocoque and hand-crafted aluminum panels. It featured the 4.2L V8 engine from the 8C Competizione, which made 420 horsepower and could launch the car from 0-62 mph in just 3.5 seconds, reports New Atlas. The whole car only weighed 850 kg (1,873 lbs), considerably lighter than the production 8C Competizione, which weighed in at a relatively porky 1,585 kg (3,494 lbs).

Convincing Rolls-Royce to make them a custom-built car is something that very few collectors could ever hope to do, and even fewer would have deep enough pockets to make that request a reality should they ever get the chance. However, one unnamed collector had no such issues, as they commissioned the brand to make the one-off Sweptail for a reported price of $13 million. That made it the most expensive new car ever commissioned at the time of its unveiling in 2017. Rolls-Royce says the design of the car is based on various yachts, with inspiration also taken from a handful of classic cars from the early 20th Century.

The Sweptail's biggest innovation is its single-piece glass roof, which tapers elegantly into the car's rear end. Inside, a relatively minimalist interior is accented with open-pore Paldao wood and polished Ebony. It's the ultimate one-off Rolls-Royce for the modern era, and it marked a return to coachbuilding for the brand, which had shied away from the idea in the decades prior.

Perhaps one of the most iconic concept cars of the past 20 years, the Maserati Birdcage 75th Pininfarina was built to celebrate the design studio's 75th birthday. It was developed in conjunction with Motorola and used cutting-edge 3D rendering to reduce development time to just two months. The car was based on the chassis of the MC12, reports Autoevolution, and borrowed the 6.0L naturally aspirated V12 engine from the MC12 GT1. Mated to the stock MC12's six-speed automated manual transmission, the engine was capable of sending up to 700 horsepower to the rear wheels.

The Birdcage's most striking design innovation is its one-piece canopy, which was inspired by the Ferrari Modulo concept of the Seventies. The canopy negates the need for doors, as the driver can simply lift the roof up in one piece to get in and out of the car. Pininfarina and Maserati won several awards for the Birdcage's design upon its release, including the Best Concept Award at the 2005 Geneva Motor Show and the Louis Vuitton Classic Concept Award a year later in 2006.

BMW's 2008 homage to the iconic M1 supercar caused a storm when it was first unveiled, and even today, it remains one of the brand's best-loved concepts. Car Magazine claimed to have evidence that the brand was looking to make the concept a production reality, even comparing the Hommage to the 1972 "Turbo" concept which turned out to closely preview the production M1. However, despite all the hype, a true M1 successor never arrived.

The closest production car to the M1 Hommage was the i8 hybrid sports car, and BMW has acknowledged that the i8 was "heavily influenced" by the Hommage concept. However, the i8 lacked the power and presence to be a true M1 successor, with our retrospective of the car pointing out that it packed about the same power as a BMW 440i, yet it cost three times the price. It sold reasonably well for its segment, shifting over 20,000 units before it was axed in 2020. It's just a shame that BMW couldn't have given enthusiasts what they really wanted and developed the M1 Hommage into a real production supercar instead of a stunning-yet-unobtainable one-off.

The Maybach Exelero hit the headlines when rapper Birdman (falsely) claimed to have purchased it for a whopping $8 million, but its original purpose was not as a collector's trophy, but rather a tire-testing vehicle. It was commissioned by Fulda, the German division of Goodyear, says Top Gear, to test its tires under extreme circumstances. The tire company specified that the car had to be both heavy and very powerful, and rather than try and convert one of its existing cars, Mercedes-Benz decided to create an all-new model to fulfill the brief.

Maybach had a long history with Fulda, having first built the tiremaker a one-off car for testing in 1938. When Fulda asked for a successor, then, it seemed only natural that Mercedes-Benz would utilize the Maybach brand to create it. Top Gear reports that the Exelero was based on a production Maybach 57S limousine, but with only two seats and a much longer hood. The car's engine capacity was also increased to 5.9L from 5.6L, and twin turbochargers were added to push power up to 691 horses. After a few years as a test vehicle, it was eventually acquired by Arnaud Massartic, a European entrepreneur and car collector. It was shortly after this point that Birdman claimed to have bought the car, but Motor Authority reports that the money never actually changed hands, and the unique Maybach is still under Massartic's ownership.