Peyote

One of the most well-known and well-regulated cacti is Lophophora williamsii,, commonly known as Peyote.

Illegal to grow or own, Peyote is known for its powerful psychedelic effects, thanks to high mescaline concentrations. It is only legal for use by members of Native American tribes because Peyote has long been a central aspect of Native American rituals. According to these tribes, using Peyote would often result in understanding spirits and other intangible entities. 

Hylocerus 

When someone brings up flowers, cacti do not immediately spring to mind, even though cacti flowers can be enormous and beautiful. Hylocerus undatus flower can exceed 14 inches  in length and 9 inches  in diameter. Hylocerus blooms only at night, and each flower opens only once before seeding and becoming a dragon fruit or falling off and dying. The flowers give off an extremely potent vanilla fragrance that can be overwhelming if the flower is smelled directly. 

Blossfeldia liliputana

Often growing between rocks in the Andes mountains, Blossfeldia liliputana earns its name from the land of Lilliput in the novel Gulliver's Travels, where all its citizens were tiny to Gulliver. This is because B. liliputana is the smallest cacti, maxing out at 0.5 inches (1.3 cm) in diameter. Its size, as well as its growth patterns, make this small wonder especially unique. Cacti often have a rounded growth point, yet B. liliputana grows from an indent at the center of the plant. Flowering during the summer months, B. liliputana self-fertilizes and produces seeds that are so small they easily blend in with the surrounding rock and sand. 

Turbinicarpus subterraneus

When thinking of cacti, we often think of tall, thick-stemmed plants coated in spikes, but this is often not the case. With the Turbinicarpus subterraneus, the true surprise is below the soil's surface. The small, club-like heads are supported by a tuberous root, often the same size as the exposed stems. This root allows T. subterraneus to survive long periods of drought by storing large quantities of water. Being below the surface also allows it to be cold resistant enough to endure short periods of exposure to temperatures as low as 25 °F. 

Atrichoke Cactus

Commonly referred to as Artichoke Cactus,  is the only species in the Obregonia genus. Similar to Ariocarpus  genus, Artichoke Cactus grows in a geophytic manner, with its body points spiraling from the growth point. While it does have spines, they are often shed from the plant, resulting in sparse patches of spines on the ends of the areoles. The spiraling, combined with the type of stem, results in the signature artichoke shape. Small flowers bloom from the tips of young growth in summer, resulting in an edible, fleshy fruit when fertilized and ripe.