I agree with a Crassula sp. There are a few with similar habit, including perforata, rupestris and marnieriana. Like most succulents they are hardy so treat them as succulents and it should thrive. They do tend to get untidy after a while so starting fresh every year or so helps keep them looking good. These ones do not seem to ever develop a trunk as such, just long thin stems and all the species I grow are prostrate and hang down over the edge of the pot so I'd agree it is unlikely to ever become 'bonsai' but might do as an accent plant or just grow it for what it is.