Party Hard

NOW WITH LOCAL CO-OP! In Party Hard, you play as someone who is really tired of their neighbours having loud parties. Instead of calling the police, you decide it’s a better idea to take everyone down using your faithful knife and the environment. The story of this tactical strategy follows a series of killings at parties throughout the USA.
The developers used to work mostly on casual, family-friendly games until they participated in a game jam, making the first prototype for Party Hard. TinyBuild backed up the original authors, Pinokl Games, to create a full version that is now on Steam!
Party Hard has semi-procedurally generated environments and focuses on unique ways of killing people. In the greatest traditions of stealth games, your main goal is not to get caught while silently picking off unsuspecting victims one by one. Dancing and blending in in a suspicious situation is key.
A (not)serious story that follows a series of murders throughout the USA
19 unique levels with random variations on each one
Use traps, cause explosions, become a ninja
Multiple unlock-able characters
Local co-op multiplayer
Special random events, like a bear coming in and killing everyone for you
Trigger the DEA, SWAT, paramedics or firefighters to come and ruin the party
 

The developers describe the content like this:

This Game may contain content not appropriate for all ages, or may not be appropriate for viewing at work: Frequent Violence or Gore, General Mature Content