These are the beta elements of Super Smash Bros. Golden X.
A boss that was taken from the final game was a light blue, Hand emeny named Icy Hand, who was similar to Fiery Hand. As the name states, he had ice powers. He was removed shortly after Dark Hand was added to the game.
Several playable characters were taken from the final game. These characters include Kritter, Dark Samus, and King Dedede. Instead, Kritter became an enemy in The Return of Tabuu, but the reason of King Dedede's removal is unknown.
The Assist Trophy was originally going to appear, but was removed in later development.
No Smash Ball
The Smash Ball was originally not going to appear, but was added around the same time as the Assist Trophy's removal.