Don't have a favorite camo pattern (based soely upon research as opposed to experience, for now, I am sold on ASAT) but this is a particularly interesting topic for me.
The pics BigSur posted are pretty convincing but CoHi has a really good point; solid natrual colors are probably the best bet.
Ever wonder why most prey animals, as well as predators (at least in the bird and mammal varieties) are simply shades of tan/brown, gray, and black? The most camo like animals I can think of are tigers and zebras. While they have contrasting, silhouette breaking lines, they aren't really the combinations or shades you typically see in popular camo clothing options (e.g. mossy oak, realtree, etc...).
It always fascinated me how a deer can blend in to a green forest so well. This concept really made me re-think the necessity of expensive camo patterns that might actually be doing more harm than good. Very curious to see what else y'all think about this one.