#RPGaDay2015 Day 25 - Favorite Revolutionary Game Mechanic
I think the best criteria for such a mechanic is that it indeed be revolutionary but also seem obvious - a sort of "gee, why didn't someone think of that before now?" By that criteria, I'm going to nominate the action system of Cubicle 7's Doctor Who: Adventures in Time and Space.
We'll examine a problem that emulating Doctor Who has and then we'll discuss how Cubicle 7 resolved this. The Doctor, in his over fifty year history, has never regularly carried weapons. On occasion he's been forced to make use of them, but generally speaking he defeats his opponents by outsmarting them. Role playing games have had a very difficult time modeling this. FASA's Doctor Who RPG, a game I played a lot of once upon a time, was a great game but didn't really reflect this aspect of Doctor Who.
Cubicle 7 handles this in two clever yet simple ways. First of all, their initiative system breaks order down based on what characters are doing. First go characters who are talking, then running, then doing some non-violent action (perhaps reversing the polarity of the neutron flow, and finally those who are fighting. Secondly, things like talking can do a type of "damage" - not physical, but the damage you give in a social conflict can prevent your enemy from opening fire on you. In my opinion, these simple changes to your typical RPG action scene perfectly capture the way the Doctor operates. It gives an in-game reason to talk to the Daleks. To talk circles around them. They are incredibly impressive at fighting. At withstanding verbal fencing, not so much.