Open Sorcery

Possibly the most original concept in all of gaming. Heck, all of literature. You're an elemental spirit meshed with computer code, employed as a kind of ghostbusting security system, monitoring locations and keeping people safe from supernatural entities. Even the primary puzzle form is dizzyingly original: deducing the "matter" of the intruders (what element they're made of) and their "motive" (the element that controls how they behave), from brief text descriptions and context clues. There's nothing else like this (apart from the DLC and sequel).