If I was fired by my employer for taking a couple of wine glasses at a banquet thrown by the chamber of commerce as souvenirs, could this be wrongful termination?

The only important question, unfortunately, is whether you had an employment contract. If you did, you could only be fired in accordance with the terms of that contract.

However, if you did not have a contract, you are an employee at will. As the term implies, an employee at will may be fired at will--at any time, for any reason, such as employer disapproval over you having taken the wine glasses. It does not matter if previously you have been an outstanding employee; your employer would be able to fire you over this, if it chose, in the absence of a contract to the contrary.