I like it when, in Cthulhu games, Investigators go mad. With that in mind, I'd like to give some reward for the first Investigator to go mad.
For example, perhaps, at the beginning of the next game, the player whose Investigator went mad first in the last game gets first choice of character.
I'd like something I can use both in Trail of Cthulhu and Call of Cthulhu. I'd also like something that affects the game, something more than just a social reward (a social reward would be, for example, getting the last beer).