Cleistocactus strausii
As a houseplant, the Silver Torch cactus is an easy to take care of so long as over-watering is avoided. To naturally simulate the porous effects of the sand in its native habitat, it's important to ensure that excess water will not pool in the soil, causing the roots to become water logged.
This plant’s native habitat does not have winter, but when temperatures drop to the low twenties, it can exhibit signs of tip frost. 
The Silver Torch cactus is most susceptible to 
mealybugs 
and spider mite.
Opuntia ficus-indica
The cattle industry of the Southwest United States has begun to cultivate "O. ficus-indica" as a fresh source of feed for cattle. The cactus is grown both as a feed source and a boundary fence. Cattle avoid the sharp spines of the cactus and do not stray from an area enclosed by it. The cactus pads are low in dry matter and crude protein, but useful as a supplement in drought conditions. In addition to the food value, the moisture content adequately eliminates watering the cattle and the human effort in achieving that chore.