I bought this particular Echeveria because of this particular leaf. When the leaves below it have withered, I'll probably remove it and try to propagate it, though I've never had success propagating unusual leaves.
For folks interested in carunculation, that's an excellent example.
I'd suspect you'd be able to propagate it more easily if you took a lively leaf and try to propagate it from the stem tissue end. Usual conditions apply for making plants from leaves of Crassulaceae.
Heed the words of a master.... Jeff has very good advice. You will be significantly more successful growing a new plant from a leave that is fresh and has the stem end intact. I have done this several times with various Echeveria. Like any other cutting, you must allow the leaf to callous for a few days. Having said this, I find it to be much easier and more "fruitful" to behead a tall plant and allow the stump to grow new plants. They mature much faster into reasonably sized plants.
No, I've propagated from leaves before, but never from a leaf that was unlike the rest on a plant. I've tried a bifurcated Graptoveria 'Fred Ives' leaf and a convex Echeveria decora leaf, but both failed.