I have actually seen this done so don't try this at home. Place a raw egg in the microwave and watch from a distance.
The egg will eventually explode as you are meant to prick a hole in the top first. This may cause your microwave to explode.Our one at work jumped around half a meter and never worked again.
The "grapetenna" experiment. (Warning: might destroy your microwave)
- Halve a grape into two while keeping some of the peel connecting the two ends. - Microwave it.
This could possibly make plasma which is pretty cool to watch.