aka crayfish, crawdads, freshwater lobsters, yabbies? I just picked up 3 of them! A snow white (black eyed lucy!), orange, and blue. Here's a pic of the white one:
I believe the white and orange one are Procambarus clarkii (color morphs of the Red swamp crayfish), and the blue one is Cherax quadricarinatus (Australian Redclaw Yabby). They're all going into their own species aquarium, and I might try my hand at breeding them someday.