In GURPS there are a few advantages that govern when the benefits of one action can be appended or duplicated within your turn; ranging from providing additional attacks to allowing multiple repeated manoeuvres to occur simultaneously. Each of these advantages have their own operational rules, implications, and interactions; causing some missed opportunities for a more generic and complete tool to create whole new advantages with.
As such, what follows is an attempt at a new advantage called Extra Action.
Whether exceptional reflexes, tracking systems, shared body assistants or mere cinematic prowess – you can perform more in a single manoeuvre than most.
By default, Extra Actions are subject only to the restrictions of what a character is or is not permitted to perform at all – being Stunned or Unconscious (and thus unable to perform manoeuvres other tan ‘Do Nothing’) do not receive an Extra Action; otherwise, consider these extra actions able to take place at any point during the character’s turn as desired.
Where mentioned in Limitations, Enhancements or similar; consider the Extra Action to be the bonus activity provided by this advantage; and the Manoeuvre to be the action chosen by the user as their chosen manoeuvre for that turn.
Extra Attack 
You can perform one extra attack per turn. This attack is subject to no additional limitations, however the default restriction of only trading one attack per turn for a Rapid Strike or Dual-Weapon Attack still applies.
If you perform a manoeuvre such as All Out Attack, this benefit does apply to extra attacks as normal.
Common examples of Extra Attack are cinematic martial artists capable of many simultaneous attacks or rapid attacks, or independently firing weapons that trigger regardless of the user’s other actions.
Extra Concentrate 
You can perform one extra concentrate per turn.
Common examples of Extra Concentrate are savants capable of quickly processing information or magicians able to simultaneously manage multiple spells.
Extra Ready 
You can perform one extra ready per turn.
Common examples of Extra Ready are cinematic action heroes readying grenades or firearms while performing other intensive actions, or those that can quickly manipulate mechanisms and devices in combat time.
Extra Move 
You can make one additional move each turn, subject to any bonuses or limitations from sprinting, posture, or movement affecting advantages.
Common examples of Extra Move may be creatures capable of prolonged movement without interruption of other tasks such as particularly skilled centaur, or creatures whose mobility is significant enough to allow frequent reorientation.
Extra Step 
This variant of Extra Move only provides one extra step per turn; this step can be taken at any point during your turn as per standard Steps, either at the same time as an existing step, or otherwise.
Extra Aim 
You can make one additional aim action per turn.
Common examples are characters with exceptional targeting skills and gunslingers, sharpshooters quickly zeroing their aim over targets, or those able to simultaneously manage multiple targets accurately.
Extra Evaluate 
You can make one additional evaluate action per turn.
Common examples are cinematic kung-fu masters able to analyse their opponent without sacrificing their own actions, or hyper-analytical swordsmen able to size up a foe instantly.
- Co-Processor: Your action is governed by a separate ‘component’ of your nervous system – mental control or investigation effects must target your extra action separately to affect it. +20%
- Time Independent: Your action is not restricted to your own manoeuvre’s cycle. The ability may be used immediately even if the character took a Wait manoeuvre, and it may also choose to perform it’s own Wait separate to the host’s manoeuvre. +50%
- Unconscious: Your action can act and perform even if you are stunned or unconscious. +30%.
- Aligned: Your action can only work in tandem with a particular manoeuvre. The extra action may only be used if the appropriate manoeuvre is used. Eg. You may only perform an Extra Attack, when you are performing an Attack; or you may only perform an Extra Concentrate when performing a Ready. -20%
- Attentive: Your action can only be performed when you have attention to spare. You cannot perform your action when performing an All-Out Attack, All-Out Defence, or similar manoeuvre. -10%
- Exclusive: Your action can only perform its task alone. The extra action may only be used if the manoeuvre chosen cannot perform that action. Eg. You may only perform an Extra Attack, when your manoeuvre does not include an attack. -30%
- Limited: Your extra action can only be used for one specific task, such as ‘Extra Attack (Auto-Turret Only)’. -20%.
- Repeater: Your action must repeat an existing manoeuvre. You must use your extra action to ‘repeat’ an action already performed. Eg. Extra concentrate with Repeater can only be used to contribute additional concentration actions to a Concentrate manoeuvre’s effect; Extra Attack with Repeater can only be used with a weapon attacked with using an attacking manoeuvre. -10%
- Synchronous: Your extra action happens alongside your existing manoeuvre. You cannot use your extra action to ‘repeat’ an action already performed. Eg. Extra Concentrate with Synchronous could not contribute a further Concentrate to a task being affected by the Concentrate manoeuvre; Extra Attack cannot use the same weapon / hand as an attack made that turn; Extra Aim or Evaluate cannot target the same subject as an Aim or Evaluate manoeuvre. This is worth -10% if it is only unable to overlap with other Extra Actions, or -20% if it also cannot overlap with the Manoeuvre.
Remade GURPS Basic Advantages
- Extra Attack (Basic) [24/level] – Extra Action (Attack) I , Aligned (Attack) -20%, Synchronous -20%.
- Extra Attack (Basic) with Multi-Strike [32/level] – Extra Action (Attack) I , Aligned (Attack) -20% .
- Compartmentalised Mind (Basic) [48/level] – Extra Action (Concentrate) I , Co-Processor +20%.
- Gunslinger (Basic)  – Extra Action (Aim) III , Aligned (Attack Only) -20%, Synchronous -10%.
- Enhanced Tracking [7.2/level] – Alternate Abilities (Extra Action (Aim)  & Extra Action (Evaluate) ) , Additive -20%, Synchronous -20%.
- Altered Time Rate  – Alternate Abilities (Attack , Concentrate , Ready , Move , Aim , Evaluate ) , Cosmic +50% (Extra actions are full manoeuvres).
Most of these end up close to their original values, suggesting that this isn’t too far from balanced and viable, with Gunslinger being the only outlier – it is modelled with Aim III as it can take multiple aims per turn but none at the same target, if the user decides to use Rapid Strike or Double Attack or Dual Weapon Attack etc; however doesn’t model the reduced Acc for two-handed weapons firing at RoF 4+.
- Attack of Opportunity  – Extra Action (Attack) I , Time In dependant +50%, Attentive -10%, Limited (Only Wait to Opportunity Triggers; Must Melee Attack) -20%.
Once per turn, the character may make one free melee attack against an opponent that leaves themselves open.
- Warmachine Auto-Minigun  – Extra Action (Attack) I , Time In dependant +50%, Co-Processor (Warmachine Combat AI) +20%, Synchronous -20%, Limited (Minigun Attack Only) -20%. (gadget limitations not included)
Once per turn, Warmachine’s shoulder-mounted minigun can attack an opponent freely, including waiting for targets or performing opportunity fire as needed.
- Active Mind  – Extra Action (Concentrate) I , Exclusive -30%.
The character’s mind is always tuned and ready – irrespective of their chosen combat manoeuvre, they always receive one Concentrate action per turn. This does not stack with taking the Concentrate manoeuvre.