For the purposes of these questions, you must spend this money on yourself -- it is not to be donated to charity or given to needy friends, though if you have a partner or a family, you may use it for things that benefit them as well as yourself, such as a holiday for two.
If you unexpectedly received $10... I'd go to the movies and not worry about it being in the evening.
If you unexpectedly received $100... I'd blow it on DVDs and/or CDs and/or books.
If you unexpectedly received $1,000... I'd buy a good laptop computer and possibly some software.
If you unexpectedly received $10,000... I'd pay off my student loans and use the rest to pay off a chunk of my car.
If you unexpectedly received $100,000... I'd use it as a down payment on a house.
If you unexpectedly received $1,000,000... I'd buy a house, fully, where I want one, or get the land and have a house built. I'd quit this job and start looking for one near my new house. Left overs would be used to furnish the place and build some out buildings I want.
Of course, all of this is assuming that I don't have to pay any taxes on this money, either.