Erm...condoms? Is there a not-so-obvious use for them?
Although there are better choices, condoms are a small, light weight way to carry water, especially if protected by being carried in a bandanna or such.
In a survival situation it is great to find water when you need it, but if you can't take some with you for later then you have lost a huge opportunity.
I suggest one gallon freezer bags or the replacement plastic bags for drinking bladders.
Our guys used them in Iraq to protect the barrels of their rifles from sand infiltration. I suppose there a lot of possible off label uses for them.