Out of many things in 8th edition that I am excited about, the advent of Command Points (and, more specifically, useful Stratagems to spend them) is one of my favorite new additions.
Like with other parts of the revamped rules in 8th edition, I think Stratagems provide a unique yet generally balanced way to give players more agency over their armies and make gameplay in 40k more “tactical” and based around good pre-game and in-game decision-making, rather than just winning via luck or taking the most “broken” units available to your army.
Now, besides the three “core” Stratagems from the main Rule Book (re-roll a single dice, interrupt charges to fight, and auto pass a morale check, all very useful in their own right) and a few odd ones we have gotten from the FW books, the only other stratagems we have “officially” seen are the ones in the recently released Space Marine codex (though, of course, we are about to get a whole bunch more when the CSM and Grey Knight books drop, plus I expect every faction to get their own set once they get an 8th edition codex of their own).
As one of the reviewers on a 40K Podcast I listen to said, stratagems truly are the “secret sauce” which makes the codex armies powerful, flexible, and flavorful all at once. Based on that, here is a look at what I think are some of the best stratagems available only to Space Marines (provided your army is Battle-Forged and includes at least one Space Marine detachment in it) and how they can be exploited tactically on the tabletop:
 KILLSHOT — Costing only 1CP, you can use this in the shooting phase and, as long as you have a <Chapter> Predator (of any kind, including the FW Deimos variant) within 6″ of two other friendly Predators, then all three Predators can add +1 to their to Wound rolls and +1 to their damage for the rest of that phase whenever they shoot at an enemy Monster or Vehicle.
**Against any army that contains even a few Monsters and/or vehicles (which is probably 90% of the forces in the game, except maybe pure Ork Green Tide or pure Primaris foot-slogging lists), this is an exceptionally powerful stratagem and, against armies that rely on powerful LOW units like Guilliman, Wraithknights, Stormsurges, Stompas, super-Heavy tanks, Imperial Knights, etc. it can be your “ace in the hole” for defeating them. If you take three Predators with 4 x Lascannons each, that gives you a total of 12 Lascannon shots with this Stratagem…. add in a nearby Captain for re-rolls of 1s to Hit and you get an average of 9-10 Lascannon hits… against anything T8 or below (which is the VAST majority of vehicles/monsters in the game) you are wounding on 3+s, which then bumps up to a 2+ due to the Stratagem, giving an average of 7-8 wounds at AP-3… in turn, against most vehicle/monster targets with a 3+ save, that is reduced to a 6+ save, giving you 6-7 Unsaved Wounds on average. Finally, thanks to the +1 damage from this stratagem, each Lascannon wound is doing 1+D6 damage per wound, giving you an average 29!!! damage inflicted on the target after all the dust settles… that means you are potentially one-shotting things like Wraithknights and Imperial Knights, which can change the course of the game in a single shooting phase.
Even if the Predators take the Autocannon/Heavy Bolter load out instead of Lascannons (which saves points and makes them able to effectively take on mass infantry/mass light vehicles as well), activating the KILLSHOT stratagem makes them surprisingly effective against monsters and vehicles (i.e. three Predators with ACs/HBs shooting at a Wraithknight with KILLSHOT activated and a Captain nearby inflict an average of 16-17 damage in a single shooting phase… add in a nearby Lieutenant for re-rolls of 1s to Wound and that goes up to 19-20 damage, leaving the Wraithknight easy pickings to finish off with the rest of your army). The beauty of this is, like with all other Stratagems, if your opponent doesn’t have enough vehicles and/or monsters to make it worth using, then simply save the CP for something else and you can still use the Predators as a long-range fire base to support your army… I particularly like giving the three Predators Twin Lascannons and two Heavy Bolters each, since this keeps them affordable, enables them to hit hard against tough units when using KILLSHOT, and also keeps them versatile to engage the entire spectrum of enemy targets.
 AUSPEX SCAN — Costing 2 CPs, this stratagem enables an Adeptus Astartes Infantry unit to immediately make an out-of-sequence shooting attack at an enemy unit that has arrived as a reinforcement within 12″ of it as it was in the shooting phase, albeit with a -1 to its to Hit rolls (so, basically, this a new version of the old Interceptor ability from previous editions).
**I love the defensive versatility and flexibility this stratagem gives a Space Marine army, especially with the plethora of deep striking threats that exist in the current game (i.e. Tau Commanders with multiple Fusion Blasters, Scion Command squads with max Plasmas, Vanguard Vets jump packs and massed pistols/power weapons, Tyranids Mawlocs, etc.). This stratagem, while pricy in terms of CPs, gives you a highly effective way of neutralizing these threats before they “alpha strike” half of your army off the table on turn 1, especially when paired with a solid shooty infantry squad that you can use to bubble-wrap the critical elements of your force.
For example, a tactic that I have heard discussed for the upcoming CSM codex is as follows: the CSM player deep strikes a squad of 10 Terminators (all with Combi-plasmas and a PW/PF/LC) alongside a TDA Sorceror or two just outside 9″ of your army. The Sorceror(s) then cast Prescience (so more accurate shooting and no danger of overheating when the Overcharge the Plasmas) and Warp Time (so they get a free 5″ move, putting them just over 4″ away from your forces) on the Terminators and, if they need it, Death Hex on one of your units (this removes the unit’s Invul save completely for a turn)… the Terminators activate the new CSM “VETERANS OF THE LONG WAR” stratagem, giving their shooting +1 to Wound, then open up with 20 x S8 AP-3 D2 Overcharged Plasma shots, all hitting on 2+s (and with no chance of overheating) and wounding anything T7 and below on a 2+ (or anything T8 on a 3+)… with no Invul save to protect the target unit and a -3 AP value, this can basically “delete” almost any unit in your army in a single go, even Guilliman, and even if the target does survive somehow, the Terminators now only have to make a 4″ charge to successfully get into combat and finish the unit off with their specialized melee weapons.
As you can see, this can be a ridiculously potent tactic, and one that is quite difficult to defend against normally. Well, that is where the AUSPEX SCAN stratagem comes in. Say you have a unit of 5 Devastator Centurions with Grav Cannons/Hurricane Bolters and a nearby Chapter Master “bubble wrapping” the critical unit(s) in you army which your CSM opponent would want to target… as soon as the CSM Terminators drop in, before they get a chance to cast any Psychic Powers or shoot or charge, you can activate this stratagem on the Centurions and hit the Chaos Terminator squad with 20 x Grav Cannon and 60 x Hurricane Bolter shots… between the -1 to Hit from this stratagem and the re-rolls to Hit from the Chapter Master, this should inflict an average of 12 Unsaved Wounds from the Grav Cannons (or about 6 dead Terminators) and about 3-4 Unsaved Wounds from the Hurricane Bolters (or another 1-2 dead Terminators)… suddenly, from the threat of 20 super-powered Plasma shots and 10 Terminators charging down your lines, you now only have an average of 4-6 Plasma shots and 2-3 models in TDA charging you, drastically changing the situation (and, even with Ld9, those last 2-3 Terminators may quite possibly fail their morale check and run away at the end of the turn anyways, since they suffered 7-8 casualties on average from the AUSPEX SCAN shooting). This is a bit of an extreme example, but overall I think you can see the game-changing power of this stratagem, especially against powerful enemy deep striking elements that you would otherwise have a very difficult time defending against.
 STRIKE FROM THE SHADOWS (Raven Guard only) — Costing 1 CP, this stratagem allows you to set up a single RG Infantry unit in reserve and then, at the beginning of the first battle round (but before the first turn begins), set it up anywhere on the battlefield that is more than 9″ away from any enemy units (since this does not occur in any of the phases, it should not be limited to “one per phase” and thus can be used by multiple units in your army, by my interpretation).
**Another amazing stratagem which you can use to truly build your army (and your tactics) around. So, a couple of things right off the bat… the wording on this stratagem says “a Raven Guard infantry unit,” with no restrictions on what kind… this means that you can use it on anything from Tactical squads and Primaris Intercessors to Jump Pack Vanguard Veterans to even Terminators or Centurions (all types). Secondly, and equally significant, this all occurs before the first turn begins, but after any Seize the Initiative has happened, meaning that you can deploy your units with this stratagem knowing safely who has first turn. Finally, because this occurs before the first turn, this means that any units impacted by it do not count as having moved already and, when you first turn comes up, they can still make their full move (and/or advance, if required).
Taking all of this into account, there are multiple ways to exploit this stratagem: right out the gate, it allows you to deploy “reactively” with key units, meaning that you can place them on the battlefield with full knowledge already of your opponent’s deployment and what forces he has available. With a “shooty” unit like a Devastator squad or Hellblaster squad or Sternguard squad, this enables them to set up exactly where you need them and with the ability to target exactly the enemy unit you need them to engage, all without any penalties to Hit due to moving and shooting. Combine this with the Raven Guard Chapter Tactic that gives enemy units -1 to Hit when shooting at these squads at more than 12″ away and you have both a powerful alpha strike and the ability to absorb your opponent’s shooting “counterpunch” next turn, as required.
Alternately, for an assault focused unit like Vanguard Vets or Assault Terminators or Assault Centurions, this stratagem can put them just over 9″ away from enemy lines before the game begins, then on turn 1 they can make their “normal” move (so 4″ for Centurions, 5″ for Terminators, or up to 12″ for Jump Pack infantry), setting up a very achievable charge range for even the slow-moving Centurions (also putting them all within range to maximize their close-in shooting, like flamers, meltaguns, hurricane bolters, pistols, etc. prior to charging). I think an ideal “battle group” to use this stratagem on would be a Vanguard Squad kitted out with Jump Packs, and a mix of dual LCs/THs and Stormshields and Kayvaan Shrike with the “Silent Stalker” WL Trait (which he has to take if he is the WL). Using two CPs, you can set both of these units up just outside 9″ from enemy lines, then Turn 1 move them to just outside 1″ of the unit you want to charge (so no chance of failing the charge roll)… in the Assault Phase, have Shrike charge first, meaning that the enemy cannot shoot Overwatch (thanks to his WL trait) and, once they are locked in combat, have the Vanguard Vets charge as well… with Shrike giving everyone re-rolls to Hit, you should be able to tear up whatever unit they charged quite well and, once they gotten clear of that combat, use their Jump Packs in subsequent turns to set up more charges and/or seize objectives, as required.
Overall, I think the new Space Marine Codex has lots of very solid, if not excellent, stratagems in it, but these ones in particular stood out to me and are the ones that I will be looking to design my army lists around.