Follow a trail made of string while blindfolded
Ball of sting, items to be identified and imagination
Set up a trail with the string - you can make it as hard as you like, going through trees, over objects, double backing on itself etc... At several points, tie a mystery item which needs to be identified.
You could turn it into a competition by timing it - maybe have another scout as a "spotter" to check the blind one isn't going to run into a tre!!