Another plant that's flowering its head off - so to speak - is Eriocyse senilis (syn. Neoporteria senilis). The flowers weren't quite open when I took this photo, but I'll try to remember to catch it when it's wide open, because that's even more striking. You'll see what I mean when I post it.
This particular plant is an older specimen we've had for many years, but they flower when quite young.
We grew up knowing this as Neoporteria gerocephala, which turned out to be an illegitimate name. Since 1994 it has been placed in Eriocyse as a result of Fred Kattermann's field work. There are three subspecies recognized, of which this is subspecies senilis.
It's a bit prone to root rot so it needs excellent drainage (doesn't everything succulent???) and judicious watering.