We've already gone over a bunch of the basics when it comes to surviving (or at least prolonging) XCOM: Enemy Unknown. But what about more advanced tactics? That's where these advanced tips come in. This article in particular is all about the soldiers; what gear compliments which class, what skills work best when paired with others, that sort of thing. This is by no means meant to signify the only successful setup, but rather to give players looking to optimize their troops' effectiveness with a few guidelines to get them started. And by all means, if you have any related questions or would like to chime in with your own loadout tips, please do so in the comments below.
[SPOILER WARNING: This guide involves the use of armor, weapons, and skills that won't be available until late in the game. If you don't want to spoil anything for yourself, please stop reading.]
Assault - A very effective equipment set for an assault soldier is Ghost Armor, an Alloy Cannon, Plasma Pistol, and Arc Thrower. Ghost Armor allows a soldier to cloak for an entire turn (so long as they don't shoot at anything), and when coupled with Run & Gun is ideal when trying to figure out where enemies are hiding without alerting them to your presence. The Alloy Cannon is simply a beast at close range, and when used in conjunction with Run & Gun can get the soldier up close for an almost inescapable blast of shrapnel. The Arc Thrower isn't necessarily essential, but when using Ghost Armor it can be very easy to get in close to stun a target. Unfortunately Run & Gun doesn't pair with the Arc Thrower, but it's still ideal for closing large distances in a hurry.
Heavy - A good loadout to consider for a heavy soldier is Titan Armor, Heavy Plasma, and a S.C.O.P.E. Titan armor is the sturdiest armor available, and is immune to poison and environmental fire damage to boot. It's not particularly mobile, but it's incredibly durable. Heavy Plasma is, of course, the nastiest of the heavy machine guns but as with all the other versions it's not remarkably accurate or frugal with ammunition. This is why I recommend the S.C.O.P.E over, say, a Nano-fiber Vest; because that extra 10% accuracy bonus can make the heavy a far more effective alien killer without resorting to using rockets prematurely.
Sniper - I've yet to find a more effective set of equipment for a sniper than Archangel Armor, a Plasma Sniper Rifle, Plasma Pistol, and a S.C.O.P.E. The rifle and S.C.O.P.E are kind of a given, but pistols are also important because a sniper's accuracy doesn't only pertain to their primary weapon. And since it's only possible for them to move and fire their rifle in the same turn with a particular skill (and the shot still suffers an accuracy penalty), the pistol is great for repositioning them and using Overwatch. The Archangel Armor is the real star, though. Everyone gets an accuracy bonus when they're positioned higher than their target, but snipers can get an even bigger bonus with the right skills. With this armor equipped, all a sniper has to do is fly straight up as high as they can and wait.
Support - My ideal set for a support soldier includes Ghost Armor, a Plasma Rifle, Medkit, and Nano-fiber Vest. Why Ghost Armor? Because it can be incredibly useful to be able to make the squad's primary healer invisible for a turn. That and it's possible, with the right skill selection, to increase a support soldier's movement distance. It's not quite as good as Run & Gun, but when coupled with invisibility it makes them a very effective scout. The Nano-fiber Vest is more of a take it or leave it thing, but another handy perk support soldiers can get is the ability to carry two items instead of one. Unfortunately it's not possible to equip two medkits, but the added durability provided by the vest can certainly help keep them alive longer. An Arc Thrower is also a perfectly reasonable choice.
Assault - As I've mentioned, it's unfortunately not possible to use an Arc Thrower along with Run & Gun (Squaddie). However, Killer Instinct (Colonel) works quite well with it as it boosts the soldier's critical damage by 50% for the rest of the turn. The catch is that it only applies to critical damage, but a number of skills such as Close and Personal (Sergeant) and Aggression (Corporal) make critical hits a lot more likely. Since I tend to push my assault soldiers into harms way I prefer to stick with the more defense-oriented skills such as Lightning Reflexes (Sergeant) and Tactical Sense (Corporal). I've also found that using Flush (Lieutenant) while another soldier, probably either a heavy or support, is suppressing the target can be very effective as Suppression not only reduces the target's movement and accuracy but grants the shooter a free shot if they attempt to move. So a successful Flush won't only damage the target but also force it out of cover, which will in turn give the suppressor a follow-up shot.
Heavy - Bullet Swarm (Corporal) is certainly a tempting skill as it gives the heavy a chance to attack twice in one turn, so long as they don't move, but I vastly prefer the accuracy bonus Holo-Targeting (Corporal) grants. Especially when paired with Suppression, which will keep a target pinned down, reduce their accuracy, and boost the other soldiers' accuracy against it. Similarly the choice between Rapid Reaction and Heat Ammo (Lieutenant) might seem easy, but note that Rapid Reaction only grants a second reaction shot if the first is a hit. And later in the campaign the chances of most target surviving the first hit are pretty slim. Conversely, getting a bonus 100% to damage against robotic enemies can be a godsend. Mayhem (Colonel) is another great skill to pair with Suppression as it grants a damage bonus. So the heavy can suppress a target, hurt it, reduce it's everything, then probably kill it if it even attempts to move.
Sniper - Squad Sight (Corporal). Forget about being able to move and fire the sniper rifle in the same turn with Snap Shot (Corporal), Squad Sight is a sniper’s best friend. Being able to move and shoot might be handy in the early stages of the campaign, but there’s an accuracy penalty associated with it. Plus there’s really no substitution for flushing out enemies with other squad members, then mopping them up from over halfway across the map. Squad Sight also works incredibly well with Damn Good Ground’s (Sergeant) higher elevation accuracy bonus and some of that Archangel Armor I mentioned previously. Pair all of that with Double Tap’s (Colonel) tendency to let the sniper fire off a second shot during their turn and you have an extremely formidable killing machine the aliens won’t ever actually see. Seriously, one of my snipers that was using this setup took out a Sectopod single-handedly in one turn.
Support - Support soldier builds can essentially go one of two ways: healing or buffing/debuffing. I prefer healing as it’s far more useful (and likely) to repair damage than prevent it. The Sprinter (Corporal) ability can be incredibly useful because it gives the support soldier a few more tiles worth of movement that can, and often does, mean the difference between getting to an injured comrade in time. Similarly, Field Medic (Sergeant) is another great way to keep the squad alive since it lets the soldier use a medkit up to three times per mission. Revive (Lieutenant) can also be incredibly handy as it not only stabilizes a downed soldier but can put them back in the fight, effectively keeping the squad at full strength. Savior (Colonel) and its bonus 4 health whenever a medkit is used, when combined with upgraded technology at the forge, means the support soldier can bring just about anyone back from the brink and keep them in top form.