Bleach

Bleach is a useful survival aid. It may be used to disinfect water (make it smell of chlorine but not burn the mouth). It may also be used to disinfect wounds. Wash as normal but make the solution stronger than you would if you were drinking it.
I have recently purchased a 60ml sample bottle of peppermint foot lotion. Once this is used up the bottle will be filled with bleach and kept with my personal emergency kit. Bleach would probably also be a useful weapon against attacking dogs if it were kept in a squeeze bottle and sprayed into the animals eyes as it approached.
My total budget for this project (including the original foot balm) is about 60p.