These are the Beta Elements in Super Smash Bros. Battle.
Happy Mask Salesman
During production of the game, Icey (t∣b∣c), the artist of the logo! asked about a new Zelda character, the Happy Mask Salesman, to the game. Thunder (t∣b∣c) declined, as he already had a Majora's Mask character, Skull Kid.
Another DK character
In the original concepts of the game, there was concept art of two other characters: these are Cranky Kong and King K. Rool. Not much is known about there concepts: however, it is known that the latter could use missiles.
Several files in the game show characters in the game that were never implemented: the files are:
"lucha"- this is very vague on what it is: however, it is implied that it is actually Hawlucha, a Pokemon from X and Y, whose Japanese name is "Luchabull". A full Moveset was found in the files;
Neutral: Flying Press
Side Special: Air Slash
Up Special: Sky Uppercut
Down Special: Roost
Final Smash: Close Combat
Hawlucha, due to the extensiveness of his character, is obviously a character who's was very developed.
"Ridley"-This can safely be assumed to be Ridley from the Metroid games. He had little data in his file, but idle sprites were found.
"AR"-This could possible be Mr. AR, the mascot of the 3DS title AR Games. Just like Ridley, he has little data, but an attack, based off of shooting AR Cards, can be found.
"Ray"- This could be Ray-Man, of his own series. He has no pre-existing data in the file.