Bird's Nest
They are particularly prized in Chinese culture due to their rarity, high nutritional value.
Cacti
You can eat some variants of cacti and various dishes including soups and desserts are made using them.
Clay
Food grade clay can be eaten and many people consume it to remove heavy metals from their body.
Crystals
Crystals that are made using sugar and food coloring can be consumed. You will generally see them as decorative materials on desserts.
Eggshells.
When boiled and baked, eggshells can be turned into an edible powder that can serve as a calcium supplement.
Paper
Eating small amount of paper is not harmful, however, it should not be a part of your diet.