This play style requires you to get five kills by throwing weapons without causing an alert at any point in between. The best level is to do Attack of the Saints - Cornfield.
There is a knife right at the beginning that you can use. Take it into the cornfield and just throw it at enemies as they walk by. If you can find the scarecrow costume, this becomes much easier because it will let you stand up and aim without being seen as long as you don't move. The scarecrow outfit should be in the first shack you come across.
