wing·nut or wing nut 
(wĭngnŭt)
(wĭngnŭt)n.
1. A nut with winglike projections for thumb and forefinger leverage in turning. Also called thumbnut.
2. Slang
a. A person with extreme or fanatical political views.
b. A crazy or eccentric person.
[Senses 2a and 2b influenced by WING, faction.]
wingnut