My favorite class in Mass Effect 2 and how I like to play it.
Soldier might seem boring to some, but what drew me to the class back in Mass Effect 1 was that it fit Shepard's personality more so than any other class available. But to each their own. So in Mass Effect 2 I of course transferred over my save data on the Xbox 360, and Soldier (while now changed) was my class once more.
Soldier is still a lot of fun in ME2, but it has it's troubles too. I will go through what powers, weapons and bonus squad power I choose to play with. I will also include general strategy at the end.
I'll start with weapons:
Heavy Pistols - This is, and forever shall be, your back up weapon. When you're low on clips and pinned down only then should your heavy pistol come out, and not before. Now like many ME2 fans I downloaded all the extra content I could grab and in one of the weapons packs is the M-5 Phalanx Pistol. It does the most base damage, second highest initial ammo capacity and deals 1.5x damage to Armor, regular damage to Barriers and Shields.
Shotguns - Either you love them, or you hate them but the shotgun is tricky to master. Personally shotguns have never been my favorite, in anything let alone Mass Effect. I tend to medium to long range in my gun fights, if I can't use effective melee I don't want to be anywhere near you. But with the DLC I mentioned earlier I found a perfect solution: the Geth Plasma Shotgun. A medium to longer range beauty, highest base damage, average ammo capacity and 1.5x effective against Barriers and Shields. Plus the best feature of this weapon is that you can charge up each shot to inflict even more damage, this charge attack does use more ammo, but if you have one shot left you're still able to charge up your shotgun!
Assault Rifles - This should come as no surprise that another DLC weapon takes this slot. The M-96 Mattock is, in my opinion, the best assault rifle in the game. Again highest base damage, reduced ammo capacity (it's only fault really), long accurate semi-automatic range and slightly better than normal effectiveness against Armor, Barriers and Shields.
Sniper Rifles - This is also a no contest zone but also one of personal choice. Hands down the best sniper rifle to use is the M-98 Widow, which is only available to you after your mission onto the Collector ship. But for a long time I also used M-29 Incisor from the DLC. Both have their strengths the Widow's being fairly obvious and the clear choice (especially for harder difficulty play throughs) but nonetheless I really enjoy the 3 fire Incisor and it is the best substitute until you can get the window later in the game.
And last Heavy Weapons - This weapon choice is filled with debate and disagreement. My choice that I outline is the one I prefer, but in terms of raw power the M-920 Cain a.k.a. the nuke, is the best option. I think all the heavy weapons are useful however and its definitely a matter of preference. My preference is the Collector Particle Beam, even on Insanity it is still a viable choice (at least I think so).
Next I will examine power choices. In ME 2 you can only level up so many skills to max on your road to level 30. So the following are my choices and why:
Adrenaline Rush, Hardened - This is the one, slows time, prevents some damage, tell your friends. But this should be obvious, whether you use that time to line up a sniper shot or pound extra damage into a heavy mech coming your way this power is a must, on all difficulties. I choose Hardened over Heightened because I prefer damage resistance, as it tends to keep me alive longer (especially on insanity).
Disruptor Ammo, Heavy - Must have, stuns mech's and Geth, rips through shields. I choose heavy to have more damage than to worry about my squad, most squad mates have good powers on their own for dealing with types of defense.
Incendiary Ammo, Inferno Ammo - Same deal as with Disruptor, but hits armor hard, stops regeneration of enemy health and causes unprotected enemies to panic. This evolved version is also superior as it causes damage to enemies on the sides of your target, thus each shot can damage 3+ opponents, doesn't get much better than that.
Combat Mastery, Shock Trooper - Again fairly obvious why you should max out this skill (for combat and the story elements). I evolve it into Shock Trooper because I like having more health, more damage resistance, you get the picture =P.
For the bonus power there's many options and it can come down to preference. But if playing a Soldier on higher difficulties it comes down to two powers you should really be choosing: Fortification vs. Geth Shield Boost.
Of these 2 Geth Shield Boost gets my vote as it stacks with other shield upgrades you get and offers quite a bit of damage resistance as a result.
So those are my choices for powers and weapons. Using those options its pretty obvious the kind of play style I have. I prefer medium to long range, preferring to hang back as long as I can picking off enemies in focused bursts of fire. When I have to be out of cover I don't want to die right away I want to absorb as much damage as I can and get to my objective/deal lethal damage back. Beyond that using Adrenaline Rush and Geth Shield Boost at the right times is a situational thing and can't be imparted in a guide.
There you have it! The soldier class, in my preferred build and how I use that build to play Mass Effect 2.