Celebrity Samuel L. Jackson once did some voiceovers for commercials of the 2004 Pontiac Grand Prix. Autoblog has managed to dig out an outtake from one of the commercials.
Head over to Autoblog to listen, and you’ll very quickly understand why the commercial never made it onto your TV screen. There are also 2 commercials voiced by him which actually made it onto TV there for comparison. Just a word of warning though, the language in the outtake isn’t work safe.