You can easily decide what options you use and what not to use. You can also easily mix these options.
Option 1. Hit Often And Deadly (HOAD)
Best for games with lots of hit points if you want game to be more deadly and combats to be quicker.
To hit result over opponent AC = weapon damage + STR (full)
To hit result less than opponent AC but 5 or over = weapon damage
To hit result 2-4 = a miss
Natural 1 = botch or how natural 1 in your game works
Option 2. Exploding Damage (ExDa)
For those who want even smaller weapons a change to be deadly with a luck.
When you roll highest possible result with any damage die roll again as a cumulative damage result. Strength damage bonus only applies once as other bonuses. This only affects the dice.
Option 3. Exploding Damage v2 (ExDa2)
A little more effective.
As above but as you score the highest possible result instead of rolling the die again add one step higher die to the damage. This extra die can also explode.
Option 4. Extra Action (Exact)
For those who want more to combat with luck but still want to keep some randomness in.
With natural 20 character gets another action to perform immediately.
Option 5. Extra Hit (Exhit)
With natural 20 character has a change to hit the same opponent again. If the opponent dies this change is lost.
Option 6. Extra Hit v2 (Exhit2)
With highest possible damage result from a die character can perform another attack against the opponent. If the opponent dies this change is lost.
Option 7. Instant Kill (InKill)
For those who want the change of death in every to hit roll.
When attacking natural 20 opponent must roll save versus death or die instantly.
Option 8. Killing Spree (KSpree)
When opponent is killed by the character he gets another action right away to attack the nearest opponent (if possible, move action possible to include or something.)
Option 9. Killing Spree v2 (Kspree2)
Same as above but after every kill character also gains +x1 damage multiplier after each kill. This damage multiplier lasts as long as the killing spree.
Option 10. Killing Spree v3 (Kspree3)
In every encounter after character succesfully kills the opponent he gets +x1 multiplier to damage. These multipliers last as long as the encounter lasts.