This would actually depend on how you would like to use the Scrafy during a battle. 
A Bulk Up Scrafty could go to either stalling with crazy Defense, or sweeping, with a few Bulk Ups, crazy Attack, with Moxie boosting it even further. 
Shed Skin would be pretty useful for a staller, so that you will probably never take damage from Poison or Burn status. 
Moxie would be useful if you want to start sweeping with some pretty decent Attack. 
I would go with Moxie, since Scrafty doesn't seem like its a very good staller. 
 - 12.12.2011 12:50am