Yume Nikki contains some unused spirites.
FC World
A huge part of the FC World is unreachable. There is also a smaller island with 4 statue's that cannot be reached in any way.
Graphics for three different FC world tree's exist, but only one of them is used. Here are the other two: File:FC 01 Tree's.png There is also a tiny little cave: File:FC 01 - kopie.png