It's almost inevitable that any kind of rare car becomes a proper, investment down the road. The world of Classic Cars is absolutely full of them. These cars (usually) start off at fairly unremarkable prices, but then they end up exploding in value. That turns them into serious blue-chip investments: cars that are extremely valuable, and will remain that way pretty much forever.We've decided to select 10 of the best rare cars that are now blue-chip investments. Most of these are European classics, think Ferrari and Jaguar, but there are a couple of examples of American muscle in there. They're all mostly from before the 1990s. What they all share is rarity value, and mindbogglingly high valuations. Jaguar E-Type (Series 1) Average Used Value: $111,534 Bring a TrailerThe Jaguar E-Type has to be one of the most iconic and most recognizable sports cars of all time. This is, after all, the car that Enzo Ferrari himself once called the most beautiful car in the world. The most desirable out of all the versions of the E-Type has to be the original Series 1. This came with a 3.8 or a 4.2-liter version of Jaguar's XK engine. Earlier cars used the 3.8, while later cars used the 4.2. Both engines have the same power output, but the 4.2-liter version has more torque. The later 4.2-liter cars were also available with a 3-speed automatic transmission, if you decided to go for the 2+2 model.Jay Leno's Garage / YouTubeThe average used value for a Series 1 E-Type is $111,534, across all its variants. Those values are still rising, too. There'll be a point where these cars will regularly fetch crazy prices, and that won't be too far in the future. Porsche 930 Turbo Average Used Value: $200,553 Bring A TrailerClassic Porsche 911s have always been a solid choice on the used market. The Porsche 930 Turbo is no exception. In fact, it's probably one of the best classic 911s you can get. This is one of the proper, early Turbos, with all the terrifying driving dynamics that come with it. These cars initially came with a 3-liter turbocharged flat-6. But, from 1978, the size of the engine went up to 3.3 liters. That version is the real performance monster, producing around 300 horsepower and 304 lb-ft of torque. That's in a car that was first offered in the late '70s.Bring a TrailerA 930 Turbo will cost you around $200,553 these days. Like all classic Porsches, that value is only continuing to go up. Some examples are selling for nearly half a million dollars, and this will only become more common with time. Chevrolet Corvette L88 (C3) Average Used Value: $251,333 MecumOver the history of the Chevrolet Corvette, there have been plenty of special models. One of the craziest of the classic Corvettes has to be the C3 L88. This followed on from the C2 version of the L88, and uses the same 427 cubic inch big-block engine. Chevrolet claimed that it had 430 hp, but this was deliberately conservative to fool the insurance companies. This car's actual output is reckoned to be over 500 hp. That amount of power in a car from the golden age of American muscle means that it's seriously fast, and seriously hard to handle.MecumYou can expect to pay just over a quarter of a million dollars for a C3 L88 Corvette. That might seem like a huge amount of money for this generation of Corvette. But, that premium is well worth it, as these cars will only go up even more in value. Lamborghini Countach 25th Anniversary Edition Average Used Value: $643,844 Bring a TrailerNo car symbolizes the supercar excesses of the '80s more than the Lamborghini Countach. While the first version of the Countach was launched back in the '70s, it was the '80s where it really came into its own. The 25th Anniversary Edition arrived at the end of that decade, and it was the most outrageous Countach to date. Its 5.2-liter V12 now produced over 450 hp, and you were expected to be able to put all that power to the road without any electronic help. This really was one of the last, proper 'old-school' supercars, before things became more sanitized throughout the '90s and '00s.Bring a Trailer Countaches have been a solid investment car for some time now. The 25th Anniversary Edition is no different. They're worth just under $650,000 on average, and those values are staying strong. Anyone who bought one while they were still cheap definitely made a fantastic decision back then. Aston Martin DB5 Average Used Value: $819,740 RM Sotheby'sThe DB5 has to be the most iconic Aston Martin of all time. Made famous through its multiple appearances in the James Bond franchise, the DB5 is one of the best of the pre-V8 Aston Martin grand tourers. Powered by a 4-liter inline-5, the standard versions of these cars had over 280 hp. The super-rare Vantage model upped that to over 320 hp, thanks to some tweaks to that engine. This made the DB5 a genuinely quick car in its day, as well as being one of the most luxurious coupes you could get.Aston MartinDB5s are now worth around $819,740 on average. That means it won't be long before the DB5 is a true million-dollar car. Considering how famous it's become since it was new, that's really not surprising. People who buy these want to feel like James Bond, and that huge amount of money may very well be worth paying just for that. BMW 507 Average Used Value: $1.6 million Bring a TrailerThe BMW 507 doesn't get a lot of attention, compared to its grand touring peers from the same era. That's quite surprising in some ways, as this has all the ingredients you could possibly want from a car like this. It's a stylish convertible, with a V8 engine and a decent amount of power for its time. It's also a model of car that's had a few famous owners over the years. These have included Elvis Presley (who bought his while he was serving in the US military in Germany, and had it imported back to his home in America when his service had finished), Ursula Andress, John Surtees and Bernie Ecclestone.Bring a Trailer The BMW 507 may fly under the radar a bit, compared to other '50s grand tourers. But, collectors absolutelyknow how great these cars are, and they seriously lust after them. As a result, 507s go for huge amounts of money when they come up for sale. These are worth an average of $1.6 million, making it easily the most expensive classic BMW model out there. Shelby Cobra 427 Average Used Value: $1.8 million MecumThere aren't many American performance cars that are better than the original Shelby Cobra. An idea born out of giving the British AC Ace sports car an American V8 heart from Ford, initial cars used a 289 cubic inch V8. Shelby soon got the bug for big block power, though, and developed the 427. As the name suggests, this has Ford's 427 cubic inch big block engine in, producing over 420 hp and 480 lb-ft of torque. All that power in a car as light and sprightly as the Cobra made it downright terrifying to drive.Legendary Motorcar / YouTubeThe Cobra 427 is worth an average of $1.8 million these days. That puts it in line with how expensive other versions of the Cobra are, as well as the exploding values of any car that's based off of prime American muscle. There really isn't anything else like the Cobra 427, and people are only going to want them more and more as time goes on. Mercedes-Benz 300 SL Gullwing Average Used Value: $2 million Bring a TrailerThere's absolutely no mistaking the silhouette of the Mercedes-Benz 300 SL Gullwing. You'd spot those famous doors a mile off. Some have argued that the Gullwing is a very early example of a supercar, and it's not hard to understand why. It's very light with quite a bit of power for how much weight it has, and does have a reputation for being difficult to handle. This means you've got to be a great driver to get the best out of it. Clearly there were enough great drivers out there who could, as the Gullwing had some proper success in racing.Jay Leno's Garage / YouTubeA Gullwing is worth around $2 million these days. That means meant it turned out to be a fantastic investment for anyone who's ended up owning one. It's a gorgeous, iconic car with proper performance, andit's proven to be a blue-chip investment? That sounds like a true win-win situation. McLaren F1 Average Used Value: $25.3 million Via: RM Sotheby'sA lot of debate has been made over what car is the greatest road car of all time. Nobody will disagree, though, that the McLaren F1 deserves to be a part of that discussion. Designed by Gordon Murray during his time at McLaren, this was supposed to be theultimate road car that the technology of the time would allow. That meant a 6.1-liter V12 that produced 627 hp, a 6-speed manual transmission and rear-wheel drive. It also had an unusual cabin layout, putting the driver in the center with two passenger seats on either side.RM Sotheby's What was the result of all that power? A top speed of as much as 240 miles per hour. That made it the fastest production car in the world until the arrival of the Bugatti Veyron. It's also still the fastest naturally aspirated production car ever made, as every production car that's gone faster than it has used forced induction.The McLaren F1 is now one of the most valuable supercars you can get. The average used value right now is $25.3 million, and prices are only going to go up. Anyone who bought these while they were still fairly reasonably priced and kept hold of them is definitely sitting on a goldmine. Ferrari 250 GTO Average Used Value: $38.5 million RM Sotheby'sWhenever the Ferrari 250 GTO is mentioned, its name is spoken in legendary tones. That's for a very good reason. This was one of the most monstrous Ferraris of the 1960s. That makes it one of the most desirable cars ever made. These cars rarely ever come up for sale. But, when they do, they sell for insane prices. The average used value for these cars is $38.5 million, and it's not unheard of for examples to sell for over $50 million.Mecum What makes this legendary Ferrari so great? It's a combination of the short-wheelbase platform, very light weight and a glorious 3-liter naturally aspirated V12 engine. That engine produces just under 300 hp, and sends all the power to the rear wheels in a purely analog setup. You've got to be a seriously great driver to be able to get the best out of the 250 GTO, and that's definitely how Enzo Ferrari himself would have wanted it.Sources: Aston Martin, BMW, Chevrolet, Classic.com, Ferrari, Lamborghini, McLaren, Mercedes-Benz, Porsche, Shelby American