Shin Megami Tensei III: Nocturne
Shin Megami Tensei III: Nocturne
In Shin Megami Tensei: Nocturne's "Vortex" prototype, character models for Maya Amano (from Persona 2: Eternal Punishment), Lisa Silverman (from Persona 2: Innocent Sin), Sid Davis (Devil Summoner), and Lucifer's design from Shin Megami Tensei II are present. In the final product, the first three characters are absent and Lucifer appears in two different designs.

Additionally, Lilith seems to have had an important role in the prototype, opening up a path for the protagonist. In the final cut, this doesn't happen and she is merely a normal enemy demon.
Contributed by HyperInuyasha
The first Magatama you get in the game has a hidden skill in it. Called "pierce", this passive skill lets your physical attacks be 100% effective on all enemies. You can only unlock this by completing the Labyrinth of Amala.
Contributed by Outofmind23
If you keep the first demon you receive, a Pixie or one of her evolved forms (High Pixie or Queen Mab), throughout the game and get her to a special door on the Fifth Kapla in the optional dungeon Labyrinth of Amala, she will evolve in to a Super Pixie.
Contributed by Outofmind23
There are three versions of Nocturne in Japan. • The original version, which was only released in Japan.
• The second version called Nocturne Maniax, which is the same as the one released in the United States, updated with the optional Labyrinth of Amala dungeon, true demon ending and Dante from the Devil May Cry series.
• The third one, which again was only released in Japan in 2008 called Nocturne Maniax Chronicle Edition. This version removed Dante from the Devil May Cry series and had Raidou Kuzunoha from the Devil Summoner series in his place. Raiduo, who is silent speaks through his cat, Gouto.
Contributed by Outofmind23