Flash Grenades are powerful support tools, disabling enemies with a blinding flash of light that stops sprinting and causes total visual impairment if the grenade goes off with the target looking at it.

Flash Grenades have a 1.5-second fuse, and do not have a contact fuse. This means they can be 'cooked' and airbursted. A full-contact blind last 5.5 seconds. This is especially nasty near objectives in the open, because airbursting the Flashbang near the target is all but guaranteed to blind anyone looking at the objective area. If the objective is inside, you can simply throw the Flashbang into the room. 

Blinding And Incapacitating Support Grenades.

Concussion Grenades are powerful stun weapons that stagger enemies caught in the blast radius. It slows their movement and causes their aim to sway wildly. A direct hit results in a 5.5-second stun. Concussion Grendaes work best with a mobile character loadouts on targets in the open. If you tag an enemy and then hit him from the side or rear while he cannot turn from the stun, you have an easy kill.

Concussion Grenades have a short fuse, but they do not detonate until they hit the ground. This means you can throw them a long way, but they cannot be airbusted. Generally, throwing "Hail Marys" with Concussion Grenades is a waste of resources. But if you need to stop a flag runner or to stagger enemies around an objective point, it can be useful.

You can use this interference to fuzz the radar of enemies entering small buildings or located near objectives. You can also use it just prior to assaulting a small building or room.

Scramblers have an additional, very useful trait: when you stand inside the Scrambler's radius, it essentially acts as the blind perk--you are invisible to air support. Note that you are not invisible to UAV or immune to CUAV use, so don't try to 'hide out' in a Scrambler field. Be aware that camping out near a deployed Scrambler can be risky if you're trying to be stealthy. The very presence of a Scrambler alerts any enemy that approaches.

The EMP Grenade has a 12-meter, radius, a 10-second duration, and a 1-second fuse. It is so powerful that it can actually destroy low-flying air support, including the Osprey Gunner, Escort Airdrop, AH-6, and Pave Low. It works equally well against I.M.S systems, any type of Sentry Gun, Assault Drone, Recon Drone, and all other types of deployed Equipment.

In addition to those powerful effects, it also disable affected players' HUDs, shutting off their radar and all other onscreen indicators (though not in Hardcore mode). EMP Grenades also inflict a bit of a Flashbang effect to targets hit with them, though not to a degree of an actual Flashbang Grenade. EMPs have a short fuse and can be airbursted. Throwing them near an objective is easy and effective, but you can't throw them particularly long distances.

Smoke is critically important in objective-based game modes, but less so in deathmatch modes. However, it can still be useful to create a screen for moving across a covered lane of fire. Note that Thermal sights can see through smoke clouds, so be wary of using Smoke to cover an objective assault if you know that an enemy with a Thermal scope has eyes on the objective. When you play objective game modes, keep a build with Smoke Grenades around at all times.

The Trophy System is a powerful new defensive tool. When deployed, it intercepts all incoming projectiles...all. As in, all types of grenades, including grenade launcher projectiles, C4, RPG rounds, SMAW and Javelin shots, Predator missiles, Reaper missiles, even AC130 cannon rounds!

The Trophy System has a range just shy of 10 meters, and can destroy only two incoming projectiles before shutting down. Gunfore or a grenade can easily disable it. Nevertheless, it's a vital new piece equipment for objective-based game modes.

While it's active, it emits a radar 'ping' every two seconds that it detects any enemies who lack the Assassin perk in its radius. Because the Portable Radar has a short range, a fast-moving enemy can traverse its detection area and be through before it sweeps the area again, so don't trust it as a perfect defensive tool.

The Portable Radar is a powerful piece of equipment for defending fixed locations, notably near objectives. Place the Radar in an out-of-the-way corner near an objective, and you're alerted to enemies sneaking into the area around it.