Bfg 6600gt Oc
 

Since the card is already out of spec, why not push it a bit more? I was a bit dissapointed when I could only reach 560MHz on the core and 1.21GHz on the memory. I see many people get to 570-580MHz. Even so, the card does has a modest increase in performance.

Link: http://www.aselabs.com/articles.php?id=171