Fate/stay night: The Extremely Abridged Series (from the visual novel by Type-Moon)
7 Masters each summon a Servant, who is the spirit of a hero from past or future given flesh. They then go to town on each other. The last pair standing gets the Holy Grail, which has Monkey's-Paw like wish granting powers. Hijinx (by which I mean 'death and horror') ensue.