Miracle cures and magic potions

[Kapitan_Phillips]

Not technically a potion, but useful none the less:

Towel:

A towel is about the most massively useful thing an interstellar hitchhiker can have. You can wrap it around you for warmth as you bound across the cold moons of Jaglan Beta…wet it for use in hand-to-hand combat…wrap it around your head to ward off noxious fumes…any man who can hitch the length and breadth of the Galaxy, rough it … win through, and still know where his towel is, is clearly a man to be reckoned with.