What shocker is your pick? Ring's choices for years past: http://boxrec.com/media/index.php/Ring_Magazine_Upset_of_the_Year
Juan Manuel Lopez KO2 Daniel Ponce De Leon Figured Lopez's career was over (ie: ruined) after his losses to Salido.
We know that Ruenroeng (who's my Fighter of the Year pick) is really good now, but I still think he deserves consideration for his upset of the very highly regarded (if only slightly more experienced) Ioka.