Kwisatz Haderach (idea)

I see the Kwisatz Haderach as the combination of all the mental disciplines used throughout the Imperium. Muad'Dib had the prana-bindu training of the Bene Gesserit. He was also a Truthsayer. He had the prescience of a Guild Navigator and the intellectual capabilities of a Mentat. He also had the Other Memory of a Reverend Mother, and was the Fremen lisan al-Gaib (the "Voice From the Outer World"). Muad'Dib was the culmination of all these disciplines.

There are a few other characters in the Dune novels I think either actual Kwisatz Haderachs, or at least, good candidates:

• Hasimir Fenring (according to the Prelude to Dune, he was almost, but not quite).
• The Tlielaxu master Ajidica, who appeared to go through some kind of Spice Agony when he overdosed on Ajidimal (another Prelude to Dune storyline).
• Alia, Muad'Dib's sister, who was born a full Reverend Mother and was ultimately driven insane by the Other Memory of her grandfather, Baron Vladimir Harkonnen.
• Leto Atreides II, the God Emperor. He was even more prescient than his father.
• The last Duncan Idaho ghola. As well as being a sexual imprinter, Swordmaster and Mentat, he had Other Memory of all the Idaho gholas who preceeded him.