Many good suggestions already made, to which I would add, not just a toilet plunger as has just been suggested, but a full set of drain rods including a rubber disc for clearing toilets.
Most toilets plungers have rather short handles, but use of a drain rod keeps ones hand further away from the waste.

With suitable brushes, drain rods can also be used for sweeping most types of flue or chimney.
Also useful for prodding and poking anything that you don't want to touch.

In addition, do not forget plenty of spares or duplicates of items liable to wear or breakage, saw blades and drill bits in particular. And small items vulnerable to loss.
Several small and reasonably cheap pocket knives are useful, in an emergency it is surprisingly easy to loose them.
Many members of these forums probably replace or upgrade pocket knives when a better model is available, don't forget to put the old ones in your emergency tool kit.