The listing, pegion peas #20 has ended.
It's a staple food crop that provides good protein. You can use the green peas like fresh peas, and the dried peas like any other dried peas, beans or lentils. (In India they are actually one of the most popular pulses. Dhal is made from pigeon peas.) The peas can also be sprouted to make them even more nutritious, and they can be ground into flour.
Leaves, flowers, seed pods and seed all make nutitious animal fodder. My chickens love the peas.
The flowers attract bees.
Pigeon peas can be frequently pruned for mulch.
Every time you prune them (and also when the plant dies) the root nodules release nitrogen that can be used by other plants.
Their open canopy shelters young, delicate plants, but lets enough light through for things to grow underneath.
A hedge makes a good windbreak.
Once established they self seed prolifically. Cut down the ones you don't really want and use as mulch. Leave the ones that grow in the right spots.