#19 Crowbar
This will come in handy if you forgot to take some stuff from your home as it might help you in breaking into a superstore to get your hands on some food, or in abandoned homes to get other supplies that are on this list and you missed to take them along with you on this adventure.
Seriously, a crow bar is necessary for many things and can be used to pry rocks, open things that are stuck, or even for use in what they were made for - changing tires!