Usually an emotional weapon. Your ability to take stabs at someone, to cut someone down.
A sword fight may refer to a recent war of words with someone. Whoever wins the fight in the dream probably has the upper hand in waking life.
Fencing can mean you are “on the fence” about something, you are “going back and forth” on a decision.
A sword can also represent your ability to sever or cut something or someone out of your life. If you are succesful in using your sword in your dream then you are making progress in ridding yourself of an unwanted element.