Diamond thermal paste? Yup, the penultimate material for thermal conductivity has been turned into thermal paste by Scottish company called Electrospell. Electrospell's Thermodime™ diamond heat transfer compound is an ultra high thermal conductivity thermal interface material composed of pure surface-modified diamond microcrystals (1-micron diameter) suspended in a special carrier fluid.
http://www.frostytech.com/permalink.cfm?NewsID=75463