This was one of my shower thoughts: what if someone from the party engages in combat out of a whim?
There is a 4 player party (classes does't matter right now) against a wizard and his guard. For the opportunity of battle, it is stated that players and the wizard are enemies. While some players are for a diplomatic solution between the wizard and the party, one of the players decides to come up to the opposing guard and stab him.
Should they roll initiative in this moment, or after the first stab? I don't think that the wizard and his guard should be surprised by this attack.