Project Touhou is a Japanese PC game series made by one man, ZUN (working under Team Shanghai Alice), and usually, nothing is left over from the beta’s. However, in Embodiment of Scarlet Devil, the sixth Touhou game, a character known as Rin Satsuki was originally meant to be a playable character, although was cut out of the final game. Her name still remains in the code, and there is only one official image of her, which originally appeared on ZUN’s website.
Update: as Susumu has make us to notice, this image did not appear on ZUN’s website. It is from the Comiket booklet that shows which doujin circles are appearing at that current event and where and when. It should also be mentioned that the picture has never been official confirmed as being her, but is widely assumed to be her, as she’s never appeared anywhere else.
Also Gabrielwoj, had found other two unused sprites in the game:
Probably, a beta sprite of Rin Satsuki. Strangely enough, it was found in Stage 1 Folder, which maybe Rin Satsuki was to be the Mid-Boss of Stage 1.
Or, it is a beta sprite of Rumia (it has similar animations on her arms, but with some different details)
Those one has been found at the EXTRA stage folder, probably, Koakuma was to be another mid-boss for the stage (or maybe ZUN only recolored the same sprites of Patchouli’s Stage [Stage 4])
Notice from the 2 Images: The white colored sprite is probably for some glow, all the sprites in the game have this “effect”.
Thanks a lot to Takoto, Susumu and Gabrielwoj for the contributions!