Overkill is an episode of the zombie rail-shooter House of the Dead series specifically developed for the Wii controls. Players point the Wii Remote to aim, B button to shoot and wiggle the remote to reload. The two main buttons are used to change weapons, and other actions such as throwing a grenade.

The game is set before the events of the first episode and it takes place in the town of Bayou City. The well-known Agent G of the series is on his first mission this time, and he teams up with the Detective Washington to fight the plague of mutants, and who they thought to be at the head of this mess: Papa Caesar.

The game, while still faithful to the spirit of the series, adopts very different tone, with the use of a vintage effect, popularized in the grindhouse movie direction. That way, the game goes over the top in different areas: violence, taunts, the scenario, all deliberately hinting at playing a B-game.

There are three main modes are available: Story Mode, Director's Cut Mode and Mini-Games. Story Mode contains the classic rail-shooter concept, divided in nine levels. Director's Cut features the same levels but enhanced and generally longer. Mini-games are mostly shoot challenges for multiple players. By playing well or unlocking some achievements, the player wins money, which can be spent on upgrading weapons or buying new ones.

The game still supports multiplayer for two players simultaneously. As a novelty, a player can carry up two different weapons.