In the the Nevada desert outside of Las Vegas during CES 2009, overclockers Sampsa & SF3D from Team Finland and Pete Hardman and Sami Makinen from AMD, use a combination of liquid nitrogen and liquid helium to reach CPU tempertures of -232 degrees Celsius in order to attain CPU clock speeds of 6.5GHz and smashing the world record for 3DMarks with 45,474 3DMarks in a test.
500 litres of liquid helium for this experiment right? ... uh
I especially enjoy the part where they pour liquid helium on to their heads. \o/