The Mercedes SLK was introduced way back in 1996, but has been extensively revised since then to keep it bang on trend. The sexy little two seater roadster, with its trademark metal folding roof has always been popular and demand still remains high, thus meaning residual values are rock solid. If you want raw power the obvious choice is the blisteringly quick AMG model which can get from 0-62mph in just 4.6 seconds. Most buyers will however opt for the smaller petrol or twin turbo diesel engines which are very refined. The cabin is plush and there are lashings of gadgets to keep almost any driver entertained. The Porsche Boxster does offer a sharper drive though.