To find the Bouncer’s Key needed to unlock the Party Contraband Case in Dead Island 2, make your way to the southeastern house in Beverly Hills.
Once there you’ll find the Party Bouncer near the pool. Take him down the loot the Bouncer’s Key. Now that you have the key, head inside the house and unlock the Party Contraband Case. As a reward, you’ll receive the Powerful Whispering Blade.