Use the following trick to easily unlock the "Super Hammer" cheat, which requires 
100 EDF kills with the sledgehammer. Go to Dust near the Chemical Depot that is by 
the Badlands. Kill a few guards, then go back out of the depot. Wait for cars to pass
by, then take them from the civilians and guerrillas. Form a wall using these cars 
with only two openings just big enough for people to fit through. Wait for the EDF 
to start coming in through the holes. Take out the sledgehammer and hit them with it.
If they start trying to bash the car wall, blow up their cars. You can use the 
sledgehammer, but it will take awhile. Try using the explosives because the kills 
do not have to be all in a row. Keep doing this until you have killed enough EDF.
Note: Do not go into the Chemical Depot.