Here is a list of items that are in the game but as yet have no recipe in game to use them on. I've broken them down by Tier.
Tier 2
Red Magnesite
Chill Coller Venom
Ground Hematite
Mother of Pearl
Blood of the Corrupt
Tier 3
Saltpeter
Chill Crawler Bile
Magnetite Powder
Blessed Palm Oil
Blackened heart Blood
Tier 4
Red Lotus Petals
Whitewood Oil
Sourmetal Salts
Golden Lotus
Black Lotus Leaf
Tier 5
Sulphered red Lotus
Vanir Firewater
Frostmint Oil
Winter Mint Dust
Fire Quartz
Spirit of Amber
Black Lotus Root
Death Cap Fungus
Pearl Dust
Sardonyx
Tier 6
There was nothing in the chart listed for this tier.