A few years ago, I acquired a deltoid-leaved dewplant, the common name for oscularia deltoides. It is so named because of the triangular, or really pyramidal, leaves that it has (deltoid being the name of that pyramidal shape).
This succulent grows best outside and can weather low and high temperatures if cared for appropriately. It grows very slowly and stays small, so it’s great for small spaces.
According to World of Succulents (a site I like to visit when trying to identify succulents), this is a native plant of South Africa.
They seem to like sunlight, and thrive in heat and cold, so I would consider the deltoid-leaved dewplant as a hardy succulent. However, it’s also somewhat fickle. It changes color to lighter green or yellow-ish or an entire arm will die for apparently no reason. So, it’s hardy but… weird. And that’s ok as long as it doesn’t completely die (and over the years it hasn’t, so all is good).