Scarab sports car, driven by A.J. Foyt, at Daytona, 1964. More info here
I love this one, the monstrous March 707 Can-Am car, driven by Chris Amon in 1970.
And something a little more modern, Oreca 03-Nissan, driven by Jody Firth, Warren Hughes, and Brendon Hartley in the 2012 Le Mans 24 Hour.