Writing a list always creates division and opinions. No matter what you leave out and put in, somebody is always going to say this or that "should've been here" and this and that "has no place here".
So what I thought I'd do is write a completely and blatantly biased list with 6 sleeper cars I personally like. And if you don't, well I hope we can still be friends.
First Gen Volvo V70 R (1996-2000)
Volvo introduced the V70 in 1996, a replacement for the widely successful 850 Estate which had been on the market since 1993. The exterior featured familiar cuts and angles, including the traditional vertical rear end, while the interior included an all-new dashboard and new seats. Volvo added the V70 XC to the line-up and the car was produced until 2000, when it was replaced by the second gen V70. Over 370,000 units were built.
In 1998, Volvo introduced the sports version of the V70, called the V70 R. The long awaited successor to the mythological 850 R was powered by a 2.3 L straight-five making 247 hp and 258 torques. Zero to sixty was dealt with in 6.8 seconds. The car looked broadly the same as the standard V70 except for a few sporty details here and there and it was available in 6 different colours (M.Y. 1998) including the gorgeous Saffron you see in the header image.
VW Passat B5.5 W8 (2001-2004)
The Volkswagen Passat B5.5, also known as Typ 3BG, is basically the face-lifted version (unveiled 2001) of the original B3, the fourth generation Passat originally introduced in 1997. Over the years, the Passat B5/B5.5 was made available with a variety of different engines but the W8 was the craziest, by far and away. The Passat W8 is exactly the sort of car that car people tend to admire because it makes zero sense, it feels like they only built it for fun. Which they probably did.
It is powered by a 4 L W8 producing 271 hp and 273 lb-ft of torque, only available with 4motion all-wheel drive. In theory, the Passat W8 was supposed to be the last ever W engine Volkswagen but in practice, VW then went on to build the W12 Phaeton and the W16 VW... Veyron. And I'm certainly happy about that.
VW Phaeton W12 (2002-2011)
I don't know what was going on with VW when they decided to introduce the Phaeton. In 2002, the idea of a big, powerful, luxurious and expensive Volkswagen saloon was... courageous. Let's call it that. The Phaeton was loosely related to the Audi A8 and both the Bentley Continental GT and Flying Spur and was available with several different engines including the wondrous 5 L V10 turbodiesel (!) and a 6-litre W12 (!!).
I love the Phaeton. It is a great car with amazing value for money and the W12 in particular is one of a kind. Powered by an wildly unnecessary 6 L W12 making 414 bhp and 406 torques, which was later upgraded and given even more power in its 2004 variant, 444 bhp and 413 torques respectively.
Audi Q7 V12 TDI (2008-2012)
Introduced in 2005, the first generation Q7 was big, broad and with an in-your-face design which most people would call ugly. I agree but I also think it looked rather striking. Not pretty or subtle but kind of amusing in its own right.
For many years, the V12 TDI was the most powerful and extreme Q7 in the line-up and what I really, really liked about it was the fact that it was a diesel. Who would do that? The whole point of a diesel is to save fuel so building a V12 diesel with 493 hp (and 738 lb-ft of torque!) is insane. And the best thing about it is that, being a diesel, you couldn't really tell how powerful it was until you saw it accelerate. And that's why I loved it.
Volkswagen Golf Mk4 R32 (2002-2003)
The Volkswagen Mk4 (also known as Typ 1J) was introduced in 1997 and it was VW's attempt to up the ante and make the Golf more upmarket. It featured decisive styling and high-quality (for the time) interior. It was sold with several different engines but the super-powerful R32 was only available for just over a year.
The reason why I love the R32, and this generation in particular, is that car enthusiasts know what it is but other road users don't because all they see is a Golf. And unlike the Mk5 R32 which did feature tuning-style additions and details here and there, the Mk4 R32 said "R32" on the front grille and had bigger wheels and... that's about it because most people wouldn't notice the slightly different wheel arches and bumpers. It was powered by a 3.2 L V6 putting out 238 bhp and 236 lb-ft of torque. The R32 could do 0 to 60 in 6.6 seconds, 6.4 with the double clutch gearbox, while the top speed was 153 mph.
Third gen Renault Clio RS (2006-2012)
The third generation Renault Clio was introduced in 2005 and it was very different from the model it replaced both in terms of interior quality and looks. The Clio RS III came with square shape and cuts and angles whereas the previous Clio had a rounded and circular shape. It was also longer, bigger and much more modern.
The RS version was unveiled in 2006 and it was the last ever Clio RS to be powered by a naturally aspirated engine. It was a 16-valve 2-litre I4 engine producing 197 hp, coupled with a 6-speed manual gearbox and capable of a top speed of 134 mph and a 0-60 time of 6.9 seconds. Even though it did come with flashier wheels and a body kit, it basically looked like any other normal Clio, especially to the eyes of people who didn't know too much about cars. All in all, I still think this is one of the best second-hand cars you can buy on a budget.