Lost Valkyrie is my entry to the 7DRL 2015 Challenge.
You can download it for Windows here.
The central idea of the game is the player's attack range. The weapon of choice throughout the game is a spear. The spear can be used to lunge (attack up to 2 tiles away) or throw (attack as far as the eye can see). Of course, throwing the spear will require the player to retrieve it if they hope to progress further.
Other ideas explored: Nordic mythology, Lovecraft, interesting monsters, and status effects.