Cannons in dreams suggests that there is something drastic that needs to be done shortly. An explosive offensive or defensive action will be done in the near future. Consider the type of vehicles that the cannon is being installed on to get some ideas on what the underlying situation may suggest. For example, is the cannon on a pirate ship, war ship, or fighter plane? They could offer you subtle clues on how to proceed with your next plans of actions.
Shooting a cannon in the dream foretells that you will soon take drastic measures to accomplish your goals. The dream is very similar to shooting a gun and could have sexual connotations.
Water cannons such as being used in protests in dreams suggests that someone will use suppressive forces to put down any opposing voices. The dream suggests that you will have bad bosses or teachers who will make you feel bad and down by voicing any opposition to their teachings or directions.
Cannonballs in dreams suggests that you are harboring anger and aggression. These balls of negativity is weighing you down. You will need to figure out to free yourself of such control.
Dreaming about laser cannon represents concentrated measures to accomplish your goals. It will take you much time and preparation to finally deciding to take an action. But once you do you will make sure that your attack counts, you feel that enough is enough, you will take care of the problem once and for all. If you are using the laser cannon to destroy a drone in the dream, it indicates that you will remove anyone who is trying to meddle with your private life.
Cannon in a Circus
To see cannon in a circus in the dream, indicates that you will do certain dangerous actions in order to express yourself. Perhaps you will let your emotions and anger take the best of you, and you will soon exhibit a show of total breakdown. Be aware that people will likely to make fun of your emotional outburst and be entertained by your display of breaking down.