if someone sent you cash anonymously what would you do?

Be very bewildered, and likely a bit uncomfortable, but I've got too many goddamned medical bills to complain too loudly so I'd throw it at one of them (or at getting some heating oil into the house) and then set about trying to figure out where it came from and why so I could pay it back when I had the means. Or like, knit them something if they didn't want it paid back, or some such thing.

Have at it.