If you have a stand alone upright freezer (i.e. without the fridge on top) and you have failed to / haven't been able to face getting round to defrosting it
until the point you can hardly get the drawers to move because of the ice:
Let nature take it's course. Empty it as much as you can and switch it off. Put a couple of large bowls on the shelves and pull the freezer out a bit so you can tip it up high enough at the front to get a saucepan under the front of it. Just leave it over night.
Water will collect in the bowls and angled base of the freezer not on the kitchen floor (important if you live above someone
else) and a couple of minutes in the morning to empty out the bowls and mop up the base with a couple of towels will clear it away. After you remove the saucepan allow the freezer to stand level for a half hour or so before turning it back on.
Then get in the habit of defrosting on a more regular basis! Never, ever try to use anything to chisel the ice from the insides.