First one looks to be Agave americana v. variegata

2nd might be A. autrovirens, a potentially beautiful species. That one has had a stressful life. 3rd Agave americana. Opuntia microdasys. The fuzzy tufts on the Opuntia have fibers called glochids that get into the skin and are nasty painful, so never touch it directly.

Keep in mind that for the most part Agaves are not true desert plants. Most species from higher elevation open oak and pine forests, so in the Mojave they do best with some shade.