It isn't often that an engine makes the front page of Wikipedia, but not many engines score as high on the Ass-Kick-O-Meter™ as the Rolls-Royce R!
In addition to powering a bunch of record-breaking racing aircraft of the 1920s and 1930s- yes, people used to pack the stands for airplane races- the 2,240-cubic-inch blown V12 R also powered Sir Malcolm Campbell's Land Speed Record-breaking Blue Bird, breaking the 300 MPH barrier at Bonneville in 1935. Rolls-Royce only made 19 of these engines, and the history of each gets a nice description in this exhaustive Wikipedia entry.