...at a person, I say, "I hope he (usually he, that is) falls into a lake!"
I have no idea WHERE I got that expression from or whey I started saying it.
In fact, I even Googled "I hope he falls into a lake" and it doesn't seem like anybody else ever uses that exclamation.
Maybe I say it because it doesn't sound too harsh...I'm not wishing death or serious injury on anybody...I just want them to fall into a lake...ruin your shoes...catch a cold...not too bad.
And still, it is just so oddly satisfying to say.
"I HOPE HE FALLS INTO A LAKE!"