From Scott Amron, the designer who brought us the super-sweet Brush & Rinse toothbrush waterfountain-maker, the Cash Money Clip is one of those why-didn't-I-think-of-that inventions. A dollar, a magnet, and a piece o' metal. (Me? I'd sacrifice a second bill and cover up the works.)
Buy it here. Or just watch the movie and hack one up yourself.