The Sicariidae family contains the well-known and dangerous Loxosceles spp. (fiddle-backs, violin spiders).
The family's other two genera, Sicarius and Hexophthalma (six-eyed sand spiders) have reputedly exceptionally cytotoxic venom, although they live in sandy deserts and rarely come into contact with humans.
Quite common in the exotic pet trade is Sicarius thomisoides (formerly terrosus). I would be particularly interested in how dangerous this species is likely to be - many are now claiming that research has shown it to be minimally dangerous. I'm not sure what work this is based on - perhaps this paper? https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2767091/