The Desert Sun has a suggestion of what to do with all your spare cactus. Make a fence! They have good ideas for using some of the taller prickly pear species, or if you prefer the more modern look they recommend a few different column cactus that will work for fences. Like the Fencepost Cactus, of course.
One first-hand account from mission days explained the cactus fence solved the problem of little suitable timber in coastal Southern California. The cactus fence was devised as a substitute. They were started by cutting paddles from well established cactus that reach the height desired. They’re inserted into the ground in a tightly spaced row where they root and grow quickly if watered. Prickly pear fences were not only perfect for containing livestock; they effectively protected the homestead from hostiles. No living thing on this Earth will penetrate a dense prickly pear hedge.
The cleanest living fences are made of fence post cactus, Pachycereus marginatus. These minimally spined upright cactus stems are ramrod straight, making the most amazing green walls. The best example I’ve ever seen was at the ethnobotanical garden in Oaxaca, Mexico where the fences are crisp and straight.
We use a giant cholla for fencing, both at the nursery and at home. Austrocylindropuntia subulata makes for a very good fence. Very spiny. Fast growing. Dangerous to try to breach. And pretty magenta flowers too. What more could you want?