The original SL-Class was mostly roadsters and small coupes with removable tops. The more modern interpretation of the car has been a lightweight sports luxury car.
Some models of the SL-Class include the 350SL from 1971 to 1980, the 450SL from 1973 to 1980, the 280SL from 1974 to 1980, the 380SL from 1980 to 1986, the 500SL from 1980 to 1986, the 300SL from 1986 to 1989, the 420SL from 1986 to 1989, the 500SL from 1986 to 1989, and the 560SL from 1986 to 1989. Most of them had V6 or V8 engines. In 1994 the line got a big facelift, and the SL600 got a massive V12.
Some of the rarer AMG versions of the SL series include the SL73 AMG, SL60 AMG, and SL55 AMG. The SL73 AMG was only sold in limited numbers in 1995 and featured a powerful 525 horsepower V12 engine.
Some of the newer models include the 2005 SL500, which retailed for $90,000 and the performance version the SL55 AMG, which retailed for $122,000. The SL65 AMG is the current leader in performance, with a twin turbo V12 making over 600 horsepower. It sells for nearly $180,000. It is a playable car in the Gran Turismo 4 video game.
These cars can be bought used, but only if you know where to look. Strangely enough, the easiest place to buy a used SL - especially a newer one - is on eBay. That's right, the world's garage sale also has listings for uber luxury sports cars.