We Will Wear Armor in the Future

In many science-fiction works most if not all soldiers and or police wear roughly as much plating as a medieval knight, though often made of plastic (technically composites) instead of metal. If a Space Marine doesn't have Powered Armor he'll still usually be wearing something more covering than a ballistic vest and helmet. Oftentimes this armor is portrayed as being completely useless, though sometimes it's stated that the armor is completely bulletproof, it's just that they're using lasers.

Might be justified in that (though most militaries prefer mobility over protection) the armour provides very reliable protection against the weapons the soldiers are up against (like plate armour at its advent in the medieval times, with the armour making its wearer very hard to injure. Once more ways to bypass it arose, to be fully armoured fell out of fashion.). Or if the armor is supposed to double as a space suit (which are already bulky and cumbersome).

As an aside, personal armour technology has improved dramatically in the last fifty years, whilst the average infantry rifle has actually become less powerful (cartridge sizes have decreased for the sake of accuracy, ergonomics, ammo capacity, and automatic fire capability). For this reason, this trope is increasingly looking like Truth in Television.

Film

 * Star Wars - The infamous stormtroopers and their predecessors the clone troopers. As well as the Mandalorians.
 * Stormtrooper armor blocks radiation, chemical and biological weapons, stun bolts, and most (non-energy) melee attacks, as well as providing general life support and environmental protection. Too bad (for the stormtroopers) that the rebels just use simple blasters. But, other sources say that while it might be penetrated by a direct blaster bolt, it would at least significantly reduce damage from the absorbed bolt, so the constantly close-ranges of combat in the movies is why the armour seems useless.
 * This is illustrated in the first battle scene in the entire series. Armored stormtroopers vs. unarmored rebel bodyguards—if a blaster bolt hits anywhere near one of the rebels, they go down, while only direct hits to storm troopers do any damage. Also, you see some stormtroopers helping up their wounded after—while none of the rebel troops seem to be even moving.
 * Starship Troopers - Making the fact that they left out the book's power armor even more obvious.
 * The armor props were sold to a lot of other productions, like Power Rangers Lost Galaxy and Firefly.
 * The colonial marines in Aliens, though apparently it doesn't provide much protection from acid blood.
 * Debatable. Hicks DID survive the acid burning. Without the armor he could have potentially been burned much worse.
 * Given the damage his breastplate sustained, he'd have died in pretty short order if he were unprotected.
 * The Fifth Element: The cops wear so much armor that they look like mobile metal bon-bons with the word "Police" stenciled on them.
 * Ditto for the Mondoshawan, assuming the mechanical-looking structures that covered them actually were armor and not their actual bodies.

Live Action TV

 * Babylon 5: Earth security forces wear armor designed to deflect energy and plasma-based weapons. There are a few variants of this, including a vest and full jacket style.
 * Farscape: The Peacekeepers use an also-space-suit variant.
 * Star Trek the Next Generation, in the first episode when Picard is put on trial by Q for the crimes of humanity there were some 21st century soldiers in body armor.
 * Given that World War III was generally acknowledged to be partly nuclear in nature, these may be radiation suits of sorts.
 * Not an actual example, but probably why the guys in The Big Bang Theory wear an excessive amount of plastic while playing paintball. That and getting hit with a paintball hurts.
 * On Firefly, the "Purple-Bellies" (as Alliance soldiers are called) get their name from the black and purple armor they wear (which seems to minimize the damage done by projectile weapons at least), while the "Brown Coats" had to make due with leather dusters and the occasional metal helmet. Guess who won the war?

Literature

 * The Lensmen universe goes in very heavily for space battle armour, and it frequently incorporates a defence shield. The effect this has on combat is to force a reversion to axes, because first-class battle armour protects against hand-held beam and projectile weapons, although not against heavier semi-portable and fixed-mount systems. When you have to go up against those, the armour is powered because it's acknowledged to be too heavy for the wearers to move unassisted.
 * This appears in several sci-fi novels and series written by David Weber including:
 * Honor Harrington.
 * The Starfire novels (co-written with Steve White).
 * The March series.
 * The Empire From the Ashes series.
 * In Fury Born

Tabletop Games

 * Most of the Warhammer 40000 armies give their troops some sort of armor, though the Imperial Guard's flak armor is commonly nicknamed "cardboard vests" or "t-shirts" due to its ineffectiveness.
 * The Imperial Guard's uniforms make seem they're just wearing armour over top clothing like normal modern soldiers, but actually, their entire uniforms are flak armour as well.
 * Or in the case of the Catachan Jungle Fighters, just t-shirts over massive muscles. Which function just as well as the armour worn by other guard troops.
 * "Carapace armour" is a significantly more effective form of armour worn by many of the Imperial Guard's elite troops, such as Stormtroopers.
 * Bonus points for the Space Marines actually referring to their Power Armor as plate mail.
 * The Eldar run about in form-fitting mesh armor, sometimes with the addition of molded composite plating, the Tau generally have pretty heavy battle armor, and the Tyranids have a variety of exoskeletal structures.
 * In GURPS the trend away from armor that started in TL 4 (1450 to 1730) starts to reverse in TL 7 (1940 to 1980) with the discovery of lightweight, bullet-resistant synthetics such as kevlar. In some TL 10+ (2075 and beyond) campaigns armor is vital, while in others weapons are so devastating that dodging or shooting first is far more important.
 * For example, disintegrator technology makes armor irrelevant because they do enormous damage and bypass most armor completely while FTL laser technology makes it so that soldiers always need to be in armor because shots can hit with deadly accuracy from tremendous range.
 * Due to the general lethality of combat in Traveller armour is all but required to survive more than a couple shots. Besides Battle Dress available armours range from practically useless leather to Combat armour that requires a laser or gauss rifle to really penetrate, there's also reflec that only defends against lasers and can be added to other types of armour. However most armour tend to be a higher tech level and much more expensive than the weapons that can pierce it.

Video Games

 * Starting with Tiberian Sun soldiers in Command and Conquer, particularly GDI, have worn plating and helmets, culminating in GDI's infantry all wearing powered armor by Tiberium Twilight.
 * Given that they're living in an increasingly-Crapsack World that is getting more and more toxic to humans, the armor is justified, given that it also contains life support systems.
 * The UNSC marines in the Halo series tend to wear more plating than their modern counterparts, especially the ODSTs. But it is not powered like the Spartan's MJOLNIR armor. The trope has gotten more pronounced as the series has progressed: in the first game, quite a few marines are wearing simple fatigues, and even the armored ones wear a relatively modest set of helmet, breastplate, and greaves. The armor set gets noticeably bulkier in Halo 3 and Halo Reach, where it's become more like standard Sci-Fi plate armor.
 * Lots of armor in Mass Effect, which also functions as a spacesuit when necessary. This is probably because mass accelerator technology has made small arms even more lethal without armour.
 * Not so much in Mass Effect 2, however, where most of your teammates do not, in fact, wear armour. Interestingly, several of the villains do.
 * In the Fallout series, being set in a Schizo-Tech Alternate Universe, armour was very popular both before and after the war, amongst individuals, companies, armies and police forces alike. Its effectiveness greatly depends on how improvised it is—you may not even feel a difference shooting the fellow in the boiled leather and shooting his unarmored buddy, but a good suit of power armor (which only the best equipped factions have access to) can make one near immune or at least highly resistant to most every day wasteland threats, including radiation.
 * The Gears wear armour so ridiculously bulky it's a wonder they can move their arms, but they're still just too badass to wear helmets. Well, the protagonists don't. And the Carmines.
 * It is revealed in the third game that most of that bulk wasn't armor, they are just that large and muscular (Marcus's biceps are two third's the width of Anya's torso).
 * The armor worn by Terran Marines in Starcraft is likewise bulky, but does come with a helmet.
 * Hilariously, the armor provides no in-game benefit as Marines have no armor value until you research upgrades.
 * However, the armor does give marines 55 health compared to the 10 health of an unarmored human.
 * Averted in the Killzone, while massive suits of powered armour do exist (their users referred to as heavies) said armour is bulky, interferes with peripheral vision and slows the wearer down considerably, as a result they aren't seen in use much, everyone makes do with rather contempory looking body armour
 * Half Life 2 is a noteable aversion of this trope, as the Combine soldiers are equipped with kevlar-like soft armor that resembles modern riot gear, in contrast to the standard Sci-Fi plate armor with Shoulders of Doom that most FPS soldier enemies tend to wear.

Web Comics

 * In SSDD it's stated that buckminster fullerene armor made conventional firearms obsolete. However, the various weapons designed to counter it all have their own disadvantages (slow firing, cumbersome, expensive, tends to explode, etc).
 * In Schlock Mercenary the Toughs begin using armor fairly early on. The low-profile powered suits they eventually settle on look a lot like cloth uniforms, but definitely function as armor. And Armor Is Useless is usually averted (when it's not, bloody dismemberment usually ensues.)
 * To elaborate they first realize they need armor after facing a squad of commandos wearing armor good against small arms, so they buy bulky powered armor that is destroyed a couple missions later. Since that armor restricted movement so much (their martial arts instructor said he'd rather fight naked) they exchanged it for low-profile suits that look exactly like regular uniforms (and are used as such), but are still powered and can stop a tank round. Now they also have heavier suits for use in boarding actions.
 * The low profile armor, along with the obvious benefits of protection, also have neat features like being able to sustain the wearer in space for short time periods, and inertic flight.

Western Animation

 * The Future Badass episode of Gargoyles, Future Tense, has all the heroes pimped out in varying degrees of future armor.
 * Dark Warrior Duck wears something like this on his patrols in a Bad Future ('Time and Punishment'). He also designed a set for Gosalyn. The tradeoff between protection and mobility is highlighted by her response to going out on patrol in it: 'Dad, I can't move.'