Engineer Abilities
Standard Engineer Kit
Engineers complete construction and repair objectives, disarm enemy HE Charges and Hack Boxes (what kind of name is this goddamn), and buff their teammates' weapon damage (by 18 percent by default). They can also plant mines and defuse enemy mines.
This seems to be the way to go if you're super into side-objectives, because goddamn look at all that poo poo.
Landmine
You can plant mines on flat surfaces, if you plant an additional mine, your original mine will disappear. Your mine's status will be displayed on your HUD so you will know if it is disarmed, tripped, or destroyed.
Extra Kevlar (R2)
Buffs teammates to give them 10% damage reduction. Cannot administer this to yourself.
Gear Head (R2)
Increases the speed at which you build and repair turrets, deploy mines, and build MG nests. Upgrading and repairing is 30% faster, while building and deploying is 20% faster.
Light Turret (R2)
Allows you to place a light turret, which fires at a medium fire rate and does 10 damage per shot. It detects a small area in front of it, but will continue to track enemies that run out of this range as long as they are in view.
Nerves of Steel (R2)
Increases the speed at which you disarm enemy explosives (not sure if this applies to HE charge objectives) by 30 percent.
Command Post Upgrade (R3)
Allows you to upgrade any command post to double its effects on your team. This is done by simply going into the class change/loadout change menu, and keeping it there while a progress bar fills. It will persist until the command post is taken by the enemy team.
Medium Turret (R3)
Lets you place a medium turret, which has a 33% higher fire rate than the light turret, with the same damage per shot. You must take Light Turret as a prerequisite.
Extra Landmine (R4)
Allows you to have two landmines active at once, instead of just one. If you try to place a third, the first one you placed will be removed.
Improved Weapon Buff (R4)
Allows you to further buff your teammate's attack power. Increases your attack power buff to an extra 33% damage instead of the original 18.
Gatling Turret (R5)
Allows you to place a gatling turret that has a 58 percent higher fire rate. Damage is still the same, and it requires the other two turret perks as prerequisites.
Operative Abilities
Standard Operative Kit
Allows standard operative abilities including completion of hack objectives, spotting enemy landmines by ironsighting over them, and disguising as enemy players.
Comms Hack (R2)
Allows you to extract tactical information from fallen enemies. When completed, will reveal enemy positions on the map for five seconds, with a 20 second cooldown between uses. Comms Hacking a downed enemy will prevent them from using the Downed Fire Ability.
Firewall Command Post (R2)
Allows operatives to upgrade command posts to require them to spend 25% more time on a capture attempt. Activated by entering the command post menu and staying there until a meter fills.
Homing Beacon (R2)
Allows you to place a red outline on an enemy for six seconds by iron sighting them. Can be used while disguised, and will be viewable by all teammates, even through walls. Will also reveal enemy operatives in disguise. Enemy operatives can also do the same to you, so be sure to look out for this one. It doesn't specify whether or not the victim gets any sort of notification when he's spotted, or if this has a cooldown.
Sticky Bomb (R2)
Lets you throw a powerful grenade (500 points to the person it is stuck to, and 120 splash) which sticks to any enemy it touches and can only be removed by their teammates. Enemies can still destroy the grenade by shooting at it while it is still on the ground. Has a 20 second cooldown.
Caltrop Grenades (R3)
Lets you throw a grenade that scatter sharp spikes that damage enemies who cross over them, unless they are moving slowly or stationary. They will not hurt teammates (presumably even with friendly fire on), and remain in the world for the length of the ability's cooldown, which is 30 seconds. Damage is calculated at 5 points per spike, to a maximum of 25 damage per second. More damage is inflicted if the victim is moving quicker (i.e. light enemies sprinting will take a lot of damage, while a heavy who is ironsighted and walking will take much less).
Hack Turret (R3)
Lets you reprogram an enemy turret to be friendly and owned by yourself. Approach from behind the turret to increase your chances of a hack (I suppose this decreases the required hack time?).
Control Turret (R4)
Allows you to take remote control of a friendly turret. To initiate control, you place a device on the turret, and then activate the ability again. You can take control from anywhere on a map, but you are helpless while controlling it. You will view the turret from a first person perspective, and (presumably) you can turn it to any angle it is capable of.
Cortex Bomb (R4)
This is a bomb. You are the bomb. When incapacitated, you have the option to detonate a bomb implanted into your head that will explode on a 1.25 second fuse, and will do 220 points of splash damage within its radius.
EMP Grenade (R5)
Allows you to throw a grenade that effectively disables any enemy turrets, mines, and player radars within its radius. It will also slow the progress of enemy hacks and HE Charges (by 50 percent). It will even disable the team-wide bonuses an enemy-held command post is giving. It has a cooldown of 30 seconds between uses, and its duration depends on what is being EMP'd.
Sticky Grenades will be delayed by 1 second.
Turrets, Command Posts, Cortex Bombs, mines, Satchel Charges, PDAs (for any sort of hacking), Hack Boxes, and radars will all be disabled for 10 seconds
Soldier's HE Charges will be delayed by 30 seconds.
It will also slow down maintenance bots for a short time.