In the previous decade, if you were a well-heeled member of the global elite with a penchant for niche supercars, you might have sprung for the Koenigsegg Agera - a bonkers, 947-horsepower bruiser from the same brilliant Swedish firm that gave us the CCX the decade prior. If that just wasn't special enough, you might instead have put your money toward the limited-run Agera RS - a lighter-weight 1,160-horsepower version of the car that produces an astonishing 1,000 pounds of downforce at 155 miles per hour.

And if that wasn't special enough? You might have bought this: the Koenigsegg Agera RSN.

With its "Josh Blue" exterior over bright blue Alcantara upholstery, its optional one-megawatt power upgrade that unleashes the same 1,341 horsepower as the groundbreaking Koenigsegg One:1, and its unique "RSN" identifiers, the Agera RSN is truly one-of-a-kind. It's also currently for sale, which is splendid news if you happen to have a few million dollars lying around, burning a hole in your wallet.

How many is "a few"? That depends. If you live in the US, you're exempt from having to pay VAT - Value Added Tax - keeping the price tag to a very reasonable $4.2 million. If you live in Europe, on the other hand, VAT adds some $800,000 US to the price - enough to buy a whole fleet of more than half-a-dozen Porsche 911s.

Of course, there's only one of you. What on earth are you going to do with a fleet of 911s? Best to have the single best supercar you can buy, and the Koenigsegg Agera RSN ranks. Once you learn to cope with the fact its steering wheel is on the wrong (right) side of the car, you'll be all set in what might be the ultimate expression of the Agera RS - once the world's fastest production car with a 278-mph top speed.

This RSN went so far as to set another speed record, hitting 242 mph at a UK VMax200 event in the hands of Koenigsegg factory driver Niklas Lilja.

Sure, $4.2 million is a lot of coin. We understand if you'll need to take a moment to mull it over. But we'd recommend making up your mind sooner than later; it's doubtful that this singularly rare supercar will go back up for sale again anytime soon.