Harry Houdini (1926), Last Wish: That his wife hold an annual seance so he could reveal himself to her.
Houdini in his later life became very interested in spiritualism and seances because of the great loss he felt upon the death of his mother. After a number of years trying to communicate with her through spiritualists, he gave up – deciding the whole thing was bunkum. In order to prove it, Houdini left his wife a secret note with 10 randomly selected words that he would communicate to her after his death. For 10 years his wife held a seance on Halloween; Houdini never turned up. (Reprinted from Listverse.com, 10 Unusual Last Wills and Testaments)