RPGs are an interesting beast; the G desires an engaging mix of strategy, design, randomness, choices at different times etc; the RP demands an interesting story.
Different styles of RPG solve these problems in different ways, playing the poles against each other, using them to mutually reinforce, I dunno, this is getting awfully philosophical.
Risk, a dice mechanic.
High level description: a die-pool RPG-style check system.
The player describes what they’re trying to do (“Climb the drainpipe”).
The GM selects a statistic that applies. These statistics are relatively static for characters, and higher is better. A 0 means that there is no chance for success; a 6 means assured success (“Athletics”).
The GM selects a difficulty for the roll. For now we’ll say they just make it up, but of course
Hack: use multicolored dice, with certain failures only defrayable in certain ways.
Hack: use exploding dice, where 6’s are a 5+a new roll, or a 1 eats an adjacent failure, etc.