A Stetsonia coryne in my collection
Stetsonia is a monotypic genus of large branching columnar cacti from Argentina and Bolivia. The only known species is Stetsonia coryne, known as the "Toothpick Cactus" for it's long fierce spines. Specimens have been noted at 30 feet tall in the wild, the branches generally not exceeding 4 inches in diameter. The flowers are white with pinkish outer petals.
Stetsonia can be cultivated the same as many other columnars, in a good draining mix. They like water in the heat of summer and grow fairly fast. I have a couple of these in pots, eventually they will go in the ground. The picture below is a nice stand of it at Bachs Cactus Nursery.