I'm a mechanical engineer by training and still occasionally do some entry level hiring in it.

My favorite question in recent years has been posing an advanced project - not unreasonably difficult, but one I know they won't have covered in school. Make it clear I don't expect them to have the answer, but have them talk through their approach to this project with me. "How would you get started?" "What would you need to know?" "What resources would you use?", etc.

For us it's been a great filter - both a gauge of their current knowledge and ability to tackle an unknown.