120 mistakes not to make

 112. Unless and if

 Unless means ‘if not’ and, therefore, it is superfluous to introduce another not into the following clause.

 • Incorrect: Unless you do not give the keys of the safe you will be shot. 

• Correct: Unless you give the keys of the safe, you will be shot. 

• Correct: If you do not give the keys of the safe, you will be shot.