Chilean dwarfs, and the reason a chunk of the hobby now believes tarantulas can be genuinely tolerant. E. sp. 'Red' built that reputation almost single-handedly.
They are small, slow, terrestrial, and unusually curious. Keepers report them walking onto an open hand rather than fleeing or threat posturing, which is not typical for anything else in this hobby and is not something I would build a routine around, but it is real. Cool temperate animals, so they do not want the tropical heat most keepers default to.
Chilean export restrictions are the whole market story. Legal wild stock does not move, so supply depends entirely on European and North American breeding, which is slow because the animals are slow. Prices have stayed stubbornly high for a two-inch spider and the taxonomy remains half-resolved, with several forms still trading on trade names.