Arctic Silver 5 is a great choice and is used by 9/10 computer power users. Personally, I opted for Notcua's NT-H1 Thermal Compund found below. It works great and my temps have never been lower. It's a bit expensive, though, but worth it. Almost $15 for 3 grams.
http://www.noctua.at/main.php?show=p...s_id=13&lng=en
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