The Hut are selling "Samurai Warriors Katana" for the Nintendo Wii for £16.95 (inc Del.)
You can get cashback on top of this (e.g. 5% Quidco, making it just £16.08)
The next best price seems to be £25.49 from PowerPlayDirect.
Samurai fight fever! Battle fierce samurai! Master eight awesome weapons. You're the hero in this first-person adventure. Ready, aim, fire! Fire projectiles to eliminate enemy ninja. Shake the Wii Remote and Nunchuk to run past deadly traps. 2 player action! Eight different mini-games for two players. Save your score and records with your Mii.