I keep a list, actually, of things I would do if lots of money abruptly came my way. A scholarship fund at Pima College and / or Northern Arizona University for men going into nursing, with preference to veterans. A library of sustainable technologies and the skills required to use them. A multi-discipline school of the sword. College funds for the red-headed cousins and their little brother.
But I think the import of this question is, what's the impulse thing, the "Woo, I have money!" thing that I'd do? The nature of the word "impulse" suggests that I don't know, and it could very well end up being hookers and blow... but knowing me, it would probably be an Indian Scout motorcycle, or something equally on the edge of practicality.