use it?

Obviously pay down debts first. Credit cars, student loans etc.

But after that what do you do? Say its 100 thousand dollars that you weren't counting on that just showed up. Do you invest it? Where do you put it in a way thats safe and responsible? Do you buy a second home and turn it into a rental? Do you pay down your home? Do you spend it all on fun? Do you pay straight up for some nice vehicles so you don't have car payments? Whats the best strategy?

What are the safest most reliable ways of growing that money in a responsible way? Mutual funds? CDs? Bonds? Money market accounts? High yield savings accounts?