This one sounds like a nasty joke you'd play on someone but it really does work.
We won't even discuss how your toilet became blocked in the first place but we've all been there.
We'll join the story where you're looking down at a toilet filled with ... water ... and you want it unblocked as soon as possible. However, if there's no plunger in the house what do you do?
1) Get an ordinary mop or toilet brush
2) Wrap the head of the mop in a plastic bag (like you'd bring your shopping home in)
3) If you have more plastic bags keep adding them until you've used three or four bags to cover the mop head or toilet brush
4) If you have a bit of string tie the tops (the handle end) around the mop or brush handle
5) Proceed to push this down firmly into the blocked toilet bowl
6) Repeat until unblocked
When I first tried this I couldn't believe it would work but trying this was worth it when weighed against leaving the toilet blocked.
It seems that the plastic bags form an air tight seal around whatever's in the bowl and act even better than a regular plunger.