Parry's Agave - Agave parryi
Like the Yuccas there are so many wonderful Agaves to choose from. One of my favorites for the garden is Parry's Agave. This one doesn't get too large (which I like) and typically forms a nice cluster. The composition and tightness of the leaves I find very appealing with this species. Different subspecies have variable leaf lengths and widths.
Saguaro - Carnegia gigantea
The absolute icon of the desert southwest; I can hardly imagine a desert garden without at least one. Despite it's reputation of being painfully slow the growth rate can be increased with careful seasonal (summer) irrigation. Specimens are available as bare-root (legally salvaged, check for permit!), container grown, or field grown in specialty nurseries.
Texas Rainbow Cactus - Echinocereus dasyacanthus
All of the "Hedgehog" cacti make outstanding low-growing garden plants. The Texas Rainbow I'm most fond of because of the shaggy but variably colored spines are in bands up the stems. The huge yellow flowers (though some individuals may have pink, orange or reddish flowers) are born in the spring and make a striking display.
Boojum - Fouquieria (Idria) columnaris
This Ocotillo relative wins the award for the most Dr. Seuss-looking plant in the garden. The upright carrot-like trunk is clothed with leaves during mild moist winters which is it's main growing season. Consequently it's only marginally hardy to winter cold. Seed grown plants are available so patience is needed to grow a large specimen in the garden...but worth the wait.
Black Spined Prickly Pear - Opuntia violacea var. macrocentra
A desert garden wouldn't be complete without at least one prickly-pear type. Amongst the group called the "purple padded prickly pears" my favorite is the Black Spined. Like the rest of the varieties the pads turn purple during the cooler weather of winter. In the spring, while the pads still retain the purple color, they're crowned with tons of yellow and red flowers.
Blue Yucca - Yucca rigida
There are so many Yuccas that make outstanding garden plants but the Blue Yucca is one of my favorites. As the name implies the leaves are wonderfully blue. Older, large, multi-branched specimens make me think of a Joshua tree on steroids. If you obtain a 5 or 15 gallon specimen make sure you plant it with plenty of space as it will get large.