Spongebob Squarepants: Underpants Slam (found Xbox Live Arcade game; 2007)
Spongebob Squarepants: Underpants Slam is a 2007 Xbox Live Arcade game released alongside Screwjumper! It is an action-puzzle game that includes the characters from the Spongebob Squarepants animated show.
Due to a lack of interest, the game's servers are still up but are often empty, and the game is no longer available for sale on the Xbox Live Marketplace.
As of March 2016, the game has been leaked.
This game could have been determined not so much as "lost" as it was "inaccessible," because many users had it downloaded on their hard-drives, but it wasn't available to those who didn't have it and wanted it.
As such, this game fell into a special in-between group of lost media, since it wasn't quite lost.
After the efforts of users Brodster and SpooferJahk, a downloadable version of the game has been preserved from a torrent link among XBLA torrents, and can be found in the Mega link below.
("You will need a modified/Jtagged Xbox 360 console to play the game, and I can confirm it works on one." -SpooferJahk)