Most low-wing aircraft have some dihedral for roll stability. The 747-8 has a sort of continuous polyhedral, which seems like a sort of refinement of ordinary dihedral, and also gives more ground clearance for outboard engines.
High-wing aircraft probably do not need dihedral, and may in fact be too stable, so some anhedral may be used to counter that.
I know of one high-wing aircraft where the designer used a very small amount of dihedral for cosmetic reasons - no technical reason at all!
