I'd probably give half of it to my mom first. 'Cause she deserves it. And then I'd pay off my school tuition and loans, and put it in the bank. God, I know, I'm so boring, but I've seriously thought about this a lot haha. Who hasn't?
ETA - actually I'd probably use most of it to buy a ton of stuff in Italy when I go in a couple of days 'cause right now I've got no money, and I'm probably going to have to eat fiber bars to sustain myself rather than delicious, authentic Italian pasta.