There are at least a half dozen Opuntias in bud or bloom now. The flowers are beautiful in shades of red, orange, yellow, salmon, purple and other color variations. The plants are wicked! Some have spines that are tiny and float in the air when the plant is bumped, such as Opuntia microdasys. Cholla cactus which looks like Opuntia, with 1" to 2" spines, was included in the genus Opuntia, but has been reclassified as a separate genus, Cylindropuntia. The spines continue to be barbed and vicious, even though they're not still, technically, "Opuntia."
There are even some Opuntia that have spines 6" to 7" long like Opuntia quemillo. The Opuntia have the widest range of any of the cacti, growing from Tierra del Fuego (South America) up into Canada. Most of them handle extreme heat, cold and even snow. If you don't want to dig post holes to erect a fence, plant a combination of Opuntias and Agaves--that will keep your neighbors out!