Shield Defense is a defensive powerset released in Issue 13, it is available to Tankers, Scrappers, and Brutes. The original information release included Stalkers in the list to get Shields, but was corrected. 
Your mastery over the shield protects you from all forms of attacks in the form of defense as well as some moderate damage resistance to most types of damage. Your training with the shield enables you to protect your nearby allies boosting their defenses.
The harder pressed you are in combat the greater your offensive abilities become. Each enemy that stands toe-to-toe with you in combat will grant you a damage bonus. The first foe you engage in melee grants the highest damage bonus, and up to 10 foes can contribute to this effect. Each foe in melee also suffer from reduced damage as your shield deflects a portion of their damage. Recharge: Slow
Your incredible reflexes allow you to position your shield to deflect incoming ranged damage. While Deflection is active you will benefit from increased Ranged and AoE defense as well as some moderate protection from Defense Debuffs. Recharge: Fast
Your mastery of the shield allows you to easily deflect melee attacks, and attacks that do get through your ironclad defenses tend to do less damage. While Active Defense is active the user will gain defense to melee attacks and some minor resistance to lethal and smashing damage. Recharge: Fast
You are able to use your shield to defend nearby allies. Any teammates who remain nearby gain a bonus to their defense. (NOTE: The defense bonus from this power is only applied to nearby team mates, but not yourself.) Recharge: Slow
When you activate this power, you gain strong resistance against most types of damage and also to Disorient, Immobilization, Hold, Knockback, Repel and Sleep effects. One with the Shield costs little Endurance to activate and increases your recovery and maximum hit points for its duration, but when it wears off you are left exhausted, and substantially drained of Endurance. Note that One With the Shield is unaffected by Attack Rate changes. Recharge: Very Long
Self +Res(Disorient, Sleep, Hold, Immobilize, Repel, Knockback, All DMG but Psi), +Recovery, +Max HP
Fighting very near your allies allows you to deflect attacks much easier. You will gain a small bonus to your melee, ranged and area of effect defense this bonus grows for each ally near you. This power is always on and costs no endurance.
You can throw all of your might behind your shield and charge through ranks of foes in the blink of an eye. Using this power allows you to teleport to a selected area to deal significant smashing damage to all foes in a long cone in front of you, most foes that are struck by your Shield Charge will be knocked down. Damage: Superior, Recharge: Very Long.
Your intense training has left you tougher than even the hardiest of heroes. You gain additional hit points and resistance to fire, cold, energy, negative energy and toxic damage sources. This power is always on and costs no Endurance.