Artichoke agave (Agave parryi). Yes, it still has spines, but it stays relatively small and won't overwhelm your garden. As long as it's in full sun, you'll get the full artichoke effect with tightly clustered leaves. In shadier spaces, the plants will open up.
You can combine these with blue or green chalk sticks (Senecio), and ghost plant (Graptopetalum) for a study in chalky blues and greens, or mix with native penstemons, Pozo Blue sage and red buckwheat (Eriogonum grande rubescens) where the agaves can be either massed or used as accents.