Radiant Dance Machines are glowing-green boots designated for Hunters. Their main talent, "The Dance", improves your slow movement while aiming. This allows a Guardian to strafe to avoid incoming fire, or quickly pop in/out of cover. Radiant Dance Machines also provide the "Heavy Weapon Ammo" perk for increased max Heavy ammo / Heavy Ammo per drop.
RDMs are 1 of 4 pairs of Exotic boots, and 1 of 2 specifically for Hunters; the other pair is Bones of Eao.