Succubi are, along with Knights, one of the most memorable enemies from Diablo I, in no small part due to their buxom (and naked) appearance, but also because of their memorable death scream. They don't have unreasonably high stats like the Knights, but they are all shooters, and since they tend to shoot constantly, the screen quickly fills up with balls of energy.
Although Succubus appear in Diablo II as well, their appearance has shifted immensely, looking more like harpies.