I find a d12 exploding critical system more fun instead of just doubling damage or rolling more damage dice – which can lead to massive pools of damage dice. The d12 (criminally underused die) plus exploding mechanic is a nice balance between chaos and simplicity.
In combat, most heroes deal +d12 damage on a natural 20. Natural 20s in combat are always consecutive, and every additional twenty applies an additional +d12, so three twenties in a row means +3d12 damage dealt. This includes advantage/disadvantage dice.
*Exploding criticals stolen from Ultraviolet Grasslands.
*d12 criticals stolen from Professor Dungeon Master.