Quick idea for an RPG, embracing the idea of play at the table being more important than a character build.
You’re really good at one thing, pretty good at one or two more things, and bad at one thing. That’s your stats.
There could be a list of Strengths and Weaknesses to choose from, but original ideas should be encouraged. Your stat shouldn’t be so broad that its useful for everything, or so specialized that its useless. The bonus would depend on what system you want to base it on. For d20, maybe +5/+2/-2 to rolls. For Dungeon World style (2d6), it would be +2/+1/-1. When the DM thinks a die roll is necessary to determine something, roll. If your strength or weakness comes into play, add the modifier.
For example, Ryu the ninja is really sneaky, and pretty good with daggers and acrobatics, but is small. Valgard the berserker is great at raging, and pretty good at hunting and leading warriors, but has a dangerous short temper.