One oddity that I like to use is a simple game called Freeform Universal. It really only has one dice roll. A 1D6 chart with three successful results and three failures. One of each has an secondary benefit, and one of each has a secondary failure. You roll 1D6, and as many additional 1D6’s as you can by convincing the GM that your character has an advantage, and subtract the same for the opponent’s situation. Pick the best result.
I don’t use it as a game by itself. Instead, I use it as a GM tool for situations that we want to get over and done now, and move on.
Example: A massive battle. I’m an experienced commander, and I have a spy who relayed key enemy plans to me, but the enemy fleet is larger. So instead of 3D6, I roll 2D6. I get a 3 and a 4. I pick the 4, which means we win. Nothing more. Nothing less. Had I only gotten the single roll I would get a 3. That’s still a win, but something bad happens too.