My smallest cactus (excluding juveniles) is this Mammillaria, which is genuinely growing sideways, not rotting and falling over. That is a 4 inch pot.
Most of the small Euphorbias around here are volunteers, like this leuconeura (growing alongside a variegated mammillaris)
This looks like a bupleurifolia hybrid (alongside 'Doris Taylor')
My smallest pot is this 2" pot, and I'm going to get that Dudleya into a 4" pot ASAP.
Smallest aloe is descoingsii, smallest Echeveria is this setosa (4" pots)
Smallest rosette of the fat-leaved succulents (not counting burrito) is this 'Jet Beads' (also 4" pot)
Smallest agave (Shoji Raijin, 8" pot) and smallest Haworthia (a small retusa clone, 6" pot).
Smallest Aeonium leaves, this a fall propagation which started with a single head (4" pot)
