WordNet sense 1 (an insane person):

madman, maniac

WordNet sense 2 (a reckless impetuous irresponsible person):

daredevil, harum-scarum, hothead, madcap, swashbuckler

WordNet sense 3 (insane and believed to be affected by the phases of the moon):

moonstruck

WordNet sense 4 (afflicted with or characteristic of mental derangement):

insane