Keep in mind that to use triggers, your GameObject must be a RigidBody

Modify all of the variables to see what different results you get

Try different combinations of actions and types to see what happens

Add more actions and types to the classes and see how your functions behave for them

Set up a test scene and use all of the item classes we created

Modify the speed variables in the projectile class to see the varying results

For melee items, add a health variable to it and create an endurance system

For projectile items, see if you can figure out how to allow the item to pass though multiple objects before destroying itself

For self items, try to add a functionality to allow multiple uses of items before they get destroyed