What is this bee/wasp nest?
This is likely a honeycomb created by some species of honey bee.

A beekeeper (Jessie Brown) from New Mexico shared to her blog the following photos of a "free form" bee hive some of her bees created:





 Photo credit: Nina Dubois 

In that instance (as well as the one mentioned here and pictured below), the beekeeper moved some "burr comb" to a new location and the bees used that moved remnant piece to build a mound-like comb. 



 Photo credit: Phillip Cairns