Infiltrator

After over 30 years, we are finally given CANON Reasonable Marines.

Infiltrators are the Vanguard Primaris line infantry unit. The holy lovechild of a Reiver and a Tactical Squad, they are geared for extended recon and stealth operations behind enemy lines, with marksman bolt carbines, smoke grenades, omni-scramblers and the ability to either take lite-Apothecaries in the form of Helix Adepts, or a comms specialist who can allow them to benefit from the buff auras of any same-Chapter Phobos HQs on the table regardless of distance. They are for all intents and purposes, Space Marines who actually act like the elite shock troops they so represent. Finally after 30 years, GW has finally broken the cycle of Space Marines being depicted as morons charging into a open battlefield, or as autistic retards that are too stubborn to be able to have some improvisation. Now every Space Marine chapter is able to field entire units of Super Spec Ops. Raven Guard and Raptors are going to love the shit out of these hombres.

Equipment

Infiltrators are all clad in Phobos-pattern armor, a variant of the Mk X Power Armor that is stripped down for lighter weight and modified with silent servos. Their backpacks are adorned with a variety of antennae and they go into battle similarly equipped to other Space Marines. Most notably, their bolt carbines have special optics that enhance their accuracy, they have smoke grenades in addition to the standard frag and krak grenades and omni-scramblers which can disrupt any kind of deep strike attack.

Additional specialists can bring additional gear, including a gauntlet medical kit/Narthecium and an Infiltrator Comms Array.

Tabletop

Infiltrators in many ways are the most disgustingly good Primaris units to exist. As Troops, they have ObSec. They can infiltrate (duh). They project a bubble forcing enemies that are set up as reinforcements to do so over 12" away, making standard deep strike charges completely impossible. Their smoke grenades gives the unit access to the Smokescreen stratagem, giving them -1 to Hit for a whole turn if the enemy fires ranged weapons at them. This adds to their already high durability as 2W marines with a 3+ save. The option exists to add a Helix Adept, which is a combat medic for the squad. The Helix Adept has a weaker version of the Apothecary's narthecium, which lets it change the damage characteristic of the unit's first failed armor save of the turn to 0. Alternatively, they can take a specialist with an Infiltrator Comms Array, and thus benefit from the re-roll auras of your Phobos Captain and Phobos Lieutenant no matter where you are on the table—so while your Captain is camping in cover with your Eliminators, and your Lieutenant is dropping into the rear with your Reivers, all of your Infiltrators can sit on their objectives and still get that extra edge in combat.

Their marksman bolt carbines are also fancy. They have a standard boltgun profile, but all unmodified To Hit rolls of 6 instantly hit and wound, letting you skip the wound roll entirely against enemies and grants a 1 in 6 chance of automatically wounding ANYTHING in the game from ork boyz to titans. Granted, AP0 means that wound isn't too likely to stick on anything whose save is better than a 4+, but it does make it more useful against things with high Toughness that a regular bolter would have trouble wounding in the first place.

In short: They are highly durable ObSec troops with solid killing power, the option to take their own personal mini-Apothecary, Infiltrate, and the ability to make enemy deep strikers around them totally unable to charge and deploy further than 12" away. They are a new gold standard for objective holding troops, and they have utility outside of that role thanks to their other rules. Their only real flaws are their difficulty in dealing with armored targets and their lack of options for dealing with foes in melee, both of which can be mitigated with proper support from other units. Also, they are expensive. Clocking in at a whopping 24 points per model and an additional 10 for the Helix Gauntlet, it might be a good idea to plan your strategy around them if you plan to take more than one squad's worth.