(nearly) every tabletop game out there uses random number generators. Those generators have even become a part of the culture and mystique surrounding RPGs in particular.
We use them as a random adjudicator of success or failure. They are the place where luck meets skill and therefore keeping the game interesting.
Lately I have been struck by how often I just need a binary choice. A simple yes or no. I am honestly surprised at myself for how often they come up, but come up they do.
So instead of rolling it, I use a deck of cards for my quick/binary resolutions.
RED/BLACK = Yes/No
During skill challenges, I also add a random variable for either good or ill at the beginning of each round. An evolving narrative that keeps everyone off their damn phones. Storyteller and highest initiative player draw and shoot for high card. Winning side gets a +1 bonus to rolls that turn.
On a Joker, the bonus becomes +2 and the players get to tell ME what happened to cause it.
We still roll dice and stuff for skill checks and combat, but sometimes it just feels more organic to use the cards. I've been told it reinforces the feeling of the encounter being evenly matched (even when it is most certainly not).
The cards also seem to enhance the skills and combat portion too by adding to the ebb and flow of a good encounter.
So there you go.
TL;DR - Optional simple rules-agnostic universal ruleset to add depth to your character interactions using only a deck of playing cards (though I recommend you go with fancy ones).
On a side note, my Kickstarter for The MasterPad draws nigh! If all five of you who read this blog (I jest, there is at least 20 of you, lol!) each buy 500 of them, I can quit my day job and make more of these for a living.