Powered suit

Overview
Power suits are special suits that give its wearers enhanced combat capabilites, ranging from increased speed, to firepower. This can become nessecary because of the wearers age, some injury, to gain superhuman strength and armoured protection. In addition to these benefits these suits can provide advantages such as built in weaponry and Stealth Camouflage. They make anyone wearing them a force to be reckoned with.

Metal Gear Solid/The Twin Snakes
Gray Fox wears an actuator suit which utilizes a supersonic motor that operates with high-frequency voltage. Whenever Fox changes position, minute electric currents in the muscle are detected and utilized to control the actuating section, giving better than human agility. He could also generate a strong electro-magnetic pulse to harm nearby enemy in Metal Gear Solid and Metal Gear Solid: VR Missions.

Metal Gear Solid 2
Olga Gurlukovich wore a Cyborg Ninja suit to hide her appearance and protect Raiden. It's similar looking to the one worn by Gray Fox.

Solidus Snake used a power suit uses a portable accelerator on the back and artificial muscle tissue to give him enhanced speed and strength. A number of sensors stretch between the surface and interior of the suit like a neural network. When these sensors detect an impact, the artificial muscle in the suit reacts instantaneously by automatically contracting and diffusing the damage. It also was equipped with tentacles or 'Snake Arms' that could fire missiles or grab opponents with in close-range combat, and sweep at their feet.

Tengu soldiers also had suits that used artificial muscle tissue.

Raiden's Skull Suit used a little bit of it, too.

Raiden can wear the exact same type of powered exoskeleton that Gray Fox wore in the Raiden(Ninja) VR missions in Substance.

Metal Gear Solid 3
Colonel Volgin used a power suit to give him the ability to generate powerful electric currents; with the suit, he could use its electricity to fire bullets without a gun or to torture unfortunate victims. It could also generate an electro-magnetic shield, strong enough to deflect bullets for a short time.

Metal Gear Solid 4
Power suits are used by the B&B Corps and by the Pieuvre Armement PMC soldiers. The B&B suits each give its members their own unique capabilites in combat; for example, the suit worn by Laughing Octopus gave her the ability to camouflauge herself and to launch mini-explosives. The suits used by Pieuvre Armement gave its soldiers increased firepower and some enhanced agility.

Raiden wore an actuator suit throughout most of the game.

Super Smash Bros. Brawl
Snake can talk to Otacon on the Codec about Samus Aran from the Metroid series, saying that he can see "a women here in a power suit..."

Gray Fox is also in the game, and can enter into fights as an Assist Trophy.