Can electromagnets be used when converting kinetic energy to electric?
The implications of being able to do that would be interesting: The stronger the magnet, the faster kinetic energy is converted into electricity, and vice-versa.
If you needed the energy in the form of magnetism, then like this you could use a physical capacitor instead of electrical (i.e. a strong spring), which could have far higher energy storage.

You could build fun things like a hybrid between a railgun and a crossbow.