Mossy Oak Treestand and Predator. Having said that my wife bought me some Under Armour stuff last year for my birthday that is RealTree AP. It's pretty nice.
The best camo is the camo most readily available from different manufacturers. My vote is for Realtree AP.
Anything thats not Realtree or Mossy Oak. I am fan of the open patterns such as Predator, ASAT, etc. However this year, I switched to Sitka and they use the Optifade. The theory behind it is sound. We'll see. I think camo, especially out of a treestand is not that important.