Other Common Skills
Icestorm contains a very limited set of actions that your troopers can perform, mostly limited to Move , BS Attack and Dodge . The full rules open up a much wider set of Common Skills that can be performed by anyone.
Infinity N3 has a wide variety of Common Skills that can be performed by any trooper, although some of them require specific types of weapons, such as Intuitive Attack and Speculative Fire.
Roughly in order of importance and how often they're used in the game:
As mentioned in the Intro, movement has some further rules, notably the General Movement Rules.
As one of the major parts of the game, Ballistic Skills has it's own section.
Likewise, Close Combat has it's own section. See also the Engaged game state which restricts a trooper's actions if they start the Order in base contact with an enemy trooper, notably that the trooper only has LoF to other troopers in base contact.
This is a special type of CC Attack that lets you kill Unconscious troops without needing to roll.
Note that the Dodge skill can be used even when not being attacked, when it will become a Normal Roll rather than a Face to Face Roll.
Some troop types are naturally less agile, so Remotes and troops on motorcycles suffer a -3 MOD and TAGs suffer a -6 MOD.
IMPORTANT - Dodge is not a Short Movement Skill so cannot be combined with other Short Skills such as BS Attack. It only gives you movement in the reactive turn, never in the active turn.
All the MODs for BS Attack also apply to Discover, so for example a TO Camo marker in cover that's in the +0 range band of 8-32" will be at -9 to Discover.
Mission 4's "Change Facing" is a combination of two Infinity rules.
Change Facing is an ARO Skill that lets a reactive trooper try to turn round if the active trooper is within their ZoC. It's like a limited Dodge in that it gives them a Face to Face Roll against incoming fire, but they suffer a -3 PH MOD and can only turn on the spot rather than moving 2". Note that the Change Facing Roll must be an unbeaten success to be able to turn. Note that the -3 MOD will stack with any Dodge MODs, so for example a TAG Changes Facing on PH-9.
Alert is a related ARO skill that lets one of your troopers with LoF shout out a warning to the rest of your force, letting them declare Change Facing AROs even if the active trooper is outside their ZoC.
Warning! is a general rule that allows troopers that didn't get an Order or ARO to turn for free at the end of the Order if anyone within their ZoC (including themselves) was attacked. Note that the attack doesn't need to hit to trigger the Warning! rule.
Choosing when to declare a Change Facing ARO or to depend on the Warning! rule is an art in itself - the Change Facing PH-3 Roll will give you a defence against incoming fire, but your roll is likely to be beaten and leave you facing the wrong way even if you survive. On the other hand if you don't react at all you can turn for free, but only if you get attacked and actually survive...
The third of the weapon-specific Common Skills, this represents letting rip with an automatic weapon to try and keep the enemy's heads down. Also an Entire Order Skill, it puts the trooper into the Suppressive Fire game state. The trooper doesn't get to fire while entering the state, so make sure you're out of sight but in a good defensive position.
A trooper in this state gets Burst 3 in ARO rather than the usual Burst 1, but there are two extra effects: The weapon's range bands are replaced by the Suppressive Fire range bands, of +0 from 0-16" and -3 from 16-24". There are no range bands beyond 24", so be careful to position your trooper where they can't be seen from range, or they'll have to drop Suppressive Fire to shoot back normally, Dodge etc. Any Face to Face Roll against the trooper in Suppressive Fire state (such as BS Attack, Dodge or CC Attack) suffers a -3 MOD. As this stacks with other MODs such as cover and TO Camouflage it can be hard to get past someone suppressing.
Suppressive Fire is cancelled if the trooper declares any other skill, so common methods for dealing with it include using a flamethrower or similar to force the trooper to Dodge or be auto-hit, throwing Grenades speculatively from out of sight etc. Another common tactic against Suppressive Fire is a Coordinated Order where you activate several troopers at once (the reacting trooper can only target one of them), but that's part of the Advanced Rules so ignore that one for now.
This is a general skill used to open and close doors etc. As a Short Movement Skill, it can be combined with another Short Movement Skill or a Short Skill such as BS Attack.
This represents the trooper sneaking across narrow gaps when the enemy's attention is elsewhere. It's an Entire Order skill that lets the trooper move once, from outside LoF to outside LoF without triggering any reactions - but woe betide you misjudge the distances, because if you end the move in sight everyone will get their AROs and they will be unopposed rolls...
These are Entire Order movement skills that allow increased movement around the battlefield. They both let the trooper move their first MOV value without need for a roll, either Climbing up a vertical surface or Jumping across gaps and over obstacles, but as Entire Order skills any enemy troopers are going to get unopposed reactions.
Note that a trooper on a vertical surface can't perform any Skills other than Climb, so make sure you don't leave troopers stranded halfway up a cliff at the end of your turn.
Jump also has it's downside - you have to declare where you're jumping to before you can measure - and if you don't have enough movement to reach the landing point you'll fall from the end of the Jump and take Falling Damage which can be extremely lethal.
Engage is a type of Dodge that lets the trooper attempt to move into base contact with the active trooper in the reactive turn. This can be very useful to let your CC troops leap into combat as someone moves past but comes with a high penalty for misjudging distances - if the active trooper isn't within the 2" range, you don't even get your PH roll to defend against any attacks from the active trooper. See also the Kinematika Special Skill which lets some troopers Dodge or Engage further.
Idle is a hold-all Short Movement Skill, it's generally used to activate the trooper on the spot so that you can see what AROs the enemy troopers declare. It's also what Skills that fail their Requirements turn into, for example if you try to declare an Engage reaction but the active trooper is too far away.
This is only usable with weapons that have the Intuitive Attack trait in their profile, and represents hosing down an area with gunfire if you suspect there's someone there. It's an Entire Order skill that lets you try to attack Camouflage and TO Camouflage markers without Discovering them first, or to attack through obscuring visibility conditions like smoke clouds. It's generally limited to Direct Template Weapons like Flamethrowers and Chain Rifles (a type of shrapnel gun).
Another skill that requires a specific weapon, Speculative Fire is an Entire Order Skill that lets your trooper throw or fire Grenades over walls at unseen enemy models. It's generally Order-intensive as you suffer a -6 MOD plus the range MODs, and your opponent still gets to Dodge, but with a -3 MOD if they can't see you. However it ignores all other MODs so can be very useful against a target with lots of stacked MODs, for example -6 for TO Camo and -3 for Partial Cover.
This is another Entire Order Skill, in this case effectively combining a Move and a BS Attack - as the name suggests, it lets a trooper temporarily lean out over a balcony, parapet or the edge of a roof or out of a window to get better LoF.
Reset is roughly the equivalent of a Dodge (without movement), but against Hacking Attacks and Comms Attacks. Until you start using Hackers it is unlikely to have much use in your games.