A lot of dirt has been dug up today! Evidence of not one but two unreleased videogames have surfaced: an Akira game for SNES and Genesis and Duke Nukem: Critical Mass for PSP.
The website Unseen 64, which tracks down media for canceled or beta games, had already been privy to the existence of a 16-bit game based on the landmark 1988 anime film (a game for Famicom actually was released). Developed by THQ, Akira was set to come to SNES and Genesis as well as Sega CD, Game Gear, and Game Boy. There didn't seem to be any actual footage of the game until it was discovered in this video from the 1994 Summer CES. It doesn't look all that hot, however — it even crashes in the clip above!
Frontline Studios' Duke Nukem: Critical Mass is a different case, as it was officially released on DS in 2011. At the time of its announcement, it was to be a multiplatform title also scheduled for PSP, but that version was shelved (a gracious move in hindsight). However, a moving image technician named David Gibson stumbled across a DVD-R containing the PSP version's code and assets in the Library of Congress. Who would have guess the Duke was so deserving of preservation in our nation's capital!