It's the Same, Now It Sucks!: One complaint about the game mode is that it tends to get repetitive after a few rounds. To compensate for this, some servers implement "point shops" to allow players to change their skin and buy gear, while others have "bonus rounds" to shake up the gameplay.
The whole premise. You're stuck at a location with a random group of strangers, one of whom wants to stab you all. The one guy with the gun is the only one capable of taking out the murderer, but may make a mistake, shoot an innocent and let you all get stabbed. Have fun.
This isn't getting into some fanmade content such as customised maps.
If you're a bystander, your only hope is to either grab as many props as possible to get your own gun (which takes time and leaves the murderer to kill you) or to stick with the gunman, who may panic and shoot you by mistaking you for the killer. And if you turn your back or get stuck in an enclosed space, you're screwed.
If you're a gunman, you're left with a choice of keeping your weapon holstered (which means the murderer can pick you off with less trouble) or walking around with your revolver out, which puts a target on your back. Similarly, you have to decide whether or not that player over there is trolling or about to stab everyone- make the wrong call and everyone may soon die.
If you're the murderer, you need to take extra care to not be seen by the gunman or any witnesses.