Every class has their unique perks which aid in fulfilling a specific role. From ammo resupplies to health packs, and rocket launchers to motion sensors, Using each and every gadget from a respective class, depending on the situation, can mean the difference between winning and losing a match. Know the tools and use them to the fullest to gain a tactical advantage over your opponent.
Assault
Ammo BoxThe Ammo resupply box allows for any and all weapons to be resupplied at specific intervals depending on the round. Standard caliber bullets resupply very quickly, while grenade and rocket shells take several seconds between each resupply. As an Assault Class, toss ammo boxes often, and watch your HUD for the flashing icon.
40mm Grenade LauncherAlthough it appears as three different models: M203, GP-25, and GL1, all Grenade Launchers effectively function the same. Use the Grenade Launcher on large clusters of enemies or for blowing a hole in the side of a building for quick access.
40mm Smoke LauncherThe Smoke Launcher uses the same apparatus as the Grenade Launcher, but simply replaces the grenade shells for smoke. This is a very underused attachment, but can be invaluable to an attacking team and can provide excellent cover for a quick arming of an M-COM.
Fun Fact: For some strange reason, DICE decided to attach a GP-25 launcher to an AR-15 weapon model for their in-game Smoke Launcher image. Something that would ordinarily not fit such a weapon.
40mm ShotgunAgain, using the same apparatus as the Grenade Launcher and Smoke Launcher, the 40mm Shotgun fires a shell filled with buckshot for those up close encounters. This attachment actually deals more damage than any of the primary shotguns in both short and longer ranges.
Engineer
Repair ToolUse the Power Drill to repair wounded vehicles and send them back to the front line. It can repair Tanks, Boats, Helicopters, Quad Bikes and even the UAV; the smaller the vehicle the quicker the repair. In a desperate situation, the Power Drill can actually be used to dismantle an enemy vehicle, but do this only as a last resort or if the vehicle is taking its final breaths.
Anti-Tank MineThe Anti-Tank Mine is the quickest and most efficient way to rid the enemy of their armor if they drive over it. Place these mines in chokepoints where an armor piece is sure to run over it, sending it and the driver up in flames.
M2 Carl GustavThe Carl Gustav has its niche in anti-personnel duties. The Swedish 84mm shell is designed to produce a huge splash damage, while dealing minimal direct impact damage. This makes it ideal for eliminating foot mobiles, but less ideal for anti-armor roles.
M136 AT4Much like the Carl Gustav, the AT4 too, has a specialize role. This anti-tank 84mm shell deals a massive amount of direct impact damage, while giving very minimal splash damage. This makes the AT4's role fall directly in line with anti-armor duties. The guidance system only enhances its ability to hit the weak spots on the armor.
RPG-7The RPG-7 falls right in the middle of the Carl Gustav and AT4, doing average splash damage and average direct impact damage. This Russian 85mm shell also suffers significant vertical drop due to gravity over range due to its slower exit speed from the barrel so a great deal of compensation is needed for firing over range.
Medic
Medic KitBy delivering this box of highly potent medicines, quick recovering in the heat of battle may be achieved to a wounded soldier. With a relatively large radius, just standing near a Medic Kit will allow and bleeding man to quickly recover and return to action.
DefibrillatorsWhen the Medic Kit just won't do the trick, the Defibrillators can resuscitate a fallen soldier and return him to action, restoring a lost ticket as well. Any Medic should be on their toes waiting for the icon to appear on the HUD and run to their teammates aid before it's too late. Defibrillation is not recommended to be performed on healthy individuals as a form of "entertainment." 
Recon
Motion SensorMotion Sensors retrieve real-time intelligence and relays it to the mini-map on the HUD. By throwing these balls, it will pick up any enemy movement in its range and give any friendly player a huge advantage in knowing their position. However, a witty enemy will hear the beeping of Motion Sensor, and may either retreat or stand still, making the Motion Sensor useless.
Mortar StrikeThis computer designator allows a player to call in a 120mm mortar strike on any given target. Used mostly against armor and emplaced Heavy Machine Guns, the Mortar Strike can be a huge asset to softening an enemy advance or defense. The Mortar Strike can also be called in against buildings to bring them crumbling down.
C4This plastic explosive can be attached to most every surface making it easy for rigging and detonation. It is a very versitile tool that is ideal for sabotaging enemy vehicles, bringing down buildings and even blowing up M-COM stations. It can be remotely detonated by the user from a safe distance.
All Kits
Combat KnifeUseful only in close quarters, the Combat Knife, though it may be trusted more than once, is a one slash kill to the jugular. Usually a knife kill could be followed up by a teabagging on the corpse of the victim.
Hand GrenadeThe frag grenade is ideal for indirect killing power, sending shrapnel in a large radius. If nothing else, the concussion will at least injure the enemy, alerting you of their position and can set up a follow up kill shot.