Many automotive players (including General Motors and Mercedes) have tried to make the Wankel engine work for them (as we all know, the AMC Pacer was originally supposed to pack rotary power), but only Mazda has really managed to make cars stuffed with the simple- yet maddeningly hard to get right- little nonreciprocating mill actually turn a profit. Just making the rotary comply with emissions requirements and get not-incredibly-sucky fuel economy has been an engineering nightmare, yet Mazda's pulled it off (well, the emissions part, anyway). Here's Mazda's corporate-slick-yet-interesting history of the rotary engine and Mazda's role in making it a successful vehicle powerplant.
History of the Rotary [Mazda.com]
Ask Jalopnik Readers: Should I Take the Cash, or the Rotary [internal]