Nerf War is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Fire a Nerf® blaster until empty at target library from at least two meters away. For each card knocked off that library, put it into its owner's graveyard and Nerf War deals ½ damage to that player. (Foam darts only.)