A list of some Unavailable Items: items that were never released formally or have since been retired from the game. Most were retired as part of the July 28th, 2015 update.
Mill
Tree/Crop
Resources
Wood / Bucket of wood
Stone
Bamboo poles
Marble
Old Bazaar
Bamboo chair
Kite
Precious gemstones
Platinum
Flowers
Coins (these items have been returned to the game as tokens used at Wishing Wellspring Island)