The premise: Each combat round, roll on the table below to determine the initiative system to be used for that round. Embrace the variability.
Variable Initiative System
Roll 1d101. Each side rolls 1d6. The side that rolls highest acts first.
2. Each player rolls 1d20. PCs act in order from highest to lowest.
3. PCs act according to Dexterity in order from highest to lowest.
4. Players draw cards and act in order from highest to lowest, but can pass their turn and act later.
5. Play proceeds clockwise around the table.
6. Play proceeds counterclockwise around the table.
7. Players put their PCs' names in a hat; the GM puts the NPCs' names in the same hat. PCs and NPCs act as their names are drawn. Those with multiple attacks get their names in the hat more than once.
8. PCs act according to the players' age: eldest to youngest.
9. PCs act according to the players' age: youngest to eldest.
10. Use a spinner to determine who acts first. The first player decides who acts second, the second player decides who acts third, and so on.