Try Pathfinder! You crit whenever you exceed the target by 10 or more, and different weapons have different crit effects. For example, a Longbow is Deadly d10 so in addition to doing double base damage you also add in a d10. Your scimitar is Forceful and Sweep, which doesn't do anything extra on a crit, but does add extra damage and a bonus to hit with multiple attacks. Perfect for a whirling dervish type character.