My favorite antique pottery has to be one of the most prized and sought-after: salt-glazed stoneware with cobalt decoration, like this trio on Live Auctioneers.
Not surprisingly, the condition of pieces impacts the price. Maker's marks and the degree of embellishment also determine value, with the fancier cobalt flourishes worth far more.
I'm liking the fraktur-like tulip design on this 2-gallon jug from Cortland:
Birds are highly-prized designs as well, as seen on this jug from Fort Edwards, NY, courtesy Louwers Antiques:
If you don't want to break the bank, there are many modern stoneware potters working with cobalt and salt glazes. Here's Rockdale Stoneware's take on the bird motif: