"Here are 4 projects we're currently working on and that you might be involved with if you work here. On a scale from 1-5 how interested would you be to work on them. Briefly explain your reasoning"

Or any variation on "here's a real problem we are actually having. Do you have any ideas about how one might go about solving it?"

and bonus worst question:

"do you have kids/what does your family life look like?"