The new combat system for dragons allows you to attack their limbs, much like Dragon's Dogma. The demo at E3 shows how taking out a leg causes the dragon to roar pitifully and start limping. The developers wanted to convey that while dragons are a vicious menace to society, they are still living creatures.
After killing Alexius, Dorian laments that a man who he used to greatly admire became so twisted.
Anti-Magical Faction: The purpose of the original Inquisition, before it joined forces with the Chantry and became the Templars and Seekers of Truth. What path the new Inquisition follows depends on your choices (and the first brand-new companion announced is a mage advocate, although one that previously supported the Chantry and the Circle system before the Templar-Mage war broke out).
Anti-Poop Socking : The time needed for your agents to complete operations passes even while you aren't playing the game. Since these operations can take several hours to complete, this feature allows players to enjoy the game without having to spend too much time playing to complete the operations.
DAI is being built on DICE's Frostbite, as opposed to the aging Eclipse Engine.
Elves were redesigned again, to look less human-with-pointy-ears than in Origins, but also less Anime-like than in Dragon Age II.
Badass Gay: Par for course with BioWare. Dorian (Tevinter mage) and Sera (elven archer) are both gay and both playable party members. They are joined by Iron Bull, the pansexual Ben-Hassrath.
Barbarian Tribe: There's a sidequest where the Inquisitor has to rescue some soldiers who were captured by Avvar barbarians. One of the Avvars, the Sky Herald, is a religious man who isn't too fond of what the other Avvars have done and can join the Inquisition if the Inquisitor closes a nearby Fade Rift for him.
Bears Are Bad News: As noted in several dev comments, bears are extremely dangerous, being responsible for a number of Total Party Kills among game testers. Great bears seem to be the size of Red Templar Behemoths, which themselves tower over normal humans.
Bee Bee Gun: It is possible to craft, upgrade, and utilize a "grenade" variety called "Jar of Bees". The final upgrade is "And Some Wasps".
Beef Gate: Though areas are open, most enemies won't scale to your level, making it hard to access a sub-region if you can't beat the monsters inhabiting it.
Benevolent Architecture: Inquisition features destructible environments. So, you can knock out supports of a bridge, causing it to collapse from under the archers standing on it, toppling pillars to create cover from ranged enemy attacks, or destroying cover the enemies themselves are using. Enemies can use this against you too though.
Some of the Red Templars have been mutated by their use of Red Lyrium. These mutations range from having red lyrium protruding from them to becoming a behemoth that is barely recognizable as having once been human.
Some of the new demons were designed to be very viscerally disturbing.
Bonus Boss: Most dragons are endgame-level encounters and are not needed to complete the game, but killing dragons allows the player to get the best crafting materials in the game.
Boss Banter: Alexius taunts the Inquisition throughout his fight.
Broken Bridge: You won't be able to access an enemy castle, for example, unless you've first recruited enough forces through quests to lay siege.
Bullet Time: Haste, a Focus spell for mages, slows down time for your enemies while allowing your squad to move normally.
The Bus Came Back: Morrigan, Leliana and Cullen from previous Dragon Age games return to serve as allies of the Inquisition. The devs have also said the Warden, Alistair, Anora, Hawke, Anders and several other characters from earlier titles may appear, depending on your world state.
The Temple of Sacred Ashes from the first game returns as the site of a major peace summit. The Breach opens right on top of it.
In Origins, Sten comments that people cannot simply be summarized like "The elves are a lithe, pointy eared people who excel at poverty." This game's character selection process contains this: "Elves are a historically oppressed people, distinguishable by their pointed ears and lithe frames."
Chain Pain: Warriors now have the option to yank opponents towards them using chains.
Civil War: The ongoing Mage and Templar War, an upheaval in Orlais foreshadowed in II and Asunder, and potential elf rebellion.
Combat, Diplomacy, Stealth: While the actual gameplay is slanted heavily towards combat, the title organization has equal access to all three modes of expanding its influence, with an Adviser attached to each one: Cullen oversees military operations, Josephine takes care of diplomatic efforts, and Leliana keeps the shadowy enterprises running.
The Conspiracy: The Inquisition is resurrected to get to the bottom of the claims that a shadowy conspiracy is behind the political strife preceding Inquisition's demonic invasion.
Continue Your Mission, Dammit!: During the mission to rescue Inquisition soldiers from the Avvars in the Fallow Mire, you come across a seemingly endless horde of undead. If you spend too long fighting them, your companions will urge you to press forward to the Avvars.
Cool Chair: One of the bonuses you get for the Deluxe Edition of the game is a throne made out of a dragon's skull.
A wide variety of ornate or otherwise nifty looking one and two handed swords are available for your party to find.
The Red Templars wield glowing red swords that bear a disturbing resemblance to Meredith's red lyrium sword from the previous game. The Red Templar Archers also get similar looking bows, which bear a slight resemblance to Irvine's demonic one from Berserk.
Coop Multiplayer: The multiplayer mode is similar to the one found in Mass Effect 3: rank-and-file agents of the Inquisition are sent in groups of four to Randomly Generated Levels to fight off waves of enemies, gaining levels and equipment. Unlike in ME3, however, the multiplayer has no impact on the single-player experience.
Crapsack World: A cataclysmic event has plunged the entire continent into turmoil, dragons are darkening the skies, and the Mage-Templar War is now just one of many wars that have claimed countless lives.
The World Is Just Awesome: Yet, in spite of all of that, one of the trailers has this from the Inquisitor to the audience, saying that the Inquisition's mission will have them traveling across the lands to many different places, both beautiful, dangerous, ancient, while showing images of various beautiful places to show the audience that yes, for all of the darkness and cynicism in the series, there are things in Thedas that are worth saving.
Cult: The Venatori are a Tevinter cult that reveres the Elder One and opposes the Inquisition.
Defector from Decadence: Dorian leaves the Tevinter Imperium due to disillusionment with his country's moral decay (The Imperium is known and criticized for practicing slavery and values greed as an admirable trait).
Deployable Cover: New spells can create walls of ice and fire that your party can hide behind.
Guilt-Based Gaming: A Bioware tradition. The first gameplay demo shows the Inquisitor deciding whether their soldiers should stay with the wounded, protect the nearby village of Crestwood, or push an assault on the attacking Red Templars. The Inquisitor picks the last one - and Crestwood is burned to the ground by the time they return.
Isometric Projection: Not technically isometric, but definitely a throwback to the isometric view in Baldur's Gate, the (PC-only) tactical overhead view from Origins returns in Inquisition for all platforms.
Hell Gate: The Breach; a tear in the Veil that separates the Fade and the mundane realm, opens in the sky, allowing demons and other monstrosities to invade.
Helmets Are Hardly Heroic: Like in the previous game, there is an option to make the headgear worn by the Inquisitor invisible to better show off the player's personal face customization. Played with similarly to the last game in that the helmet's stats and defense still apply, meaning the player will still want to wear a helmet at all times.
Nay-Theist: According to Bioware, the restored Inqusition is strictly separate from the Chantry and will even have some anti-Chantry policies.
Neck Snap: Leliana uses her legs to break the neck of her Venatori torturer.
Never Heard That One Before: The devs managed to inflict this on themselves re: 'Spanish Inquisition' jokes, and resolved not to include any in the actual game.
Nice Hat: Apart from the Inquisitor's signature helmets, it seems that absolutely badass cowboy hats will also be equippable. Vivienne has a Maleficent-style horned hat (a welcome change from previous mage headgear).
Nostalgia Level: Redcliffe Castle gets taken over by the Venatori and, like in Origins, you're tasked with reclaiming it.
Old Save Bonus: Seems to be averted for the first time in the series. Dragon Age Keep, a web application that allows players to replicate their old world states for import to eighth-gen consoles, has manual input as the default method of world state creations (though it does try to salvage as much data as it can if you uploaded your DA player profiles to any of the Origin services earlier). Since everyone can use DAK, those who jump into the series at Inquisition and choose to customize their backstory won't be at a disadvantage compared to those who recreate their personal world state from the previous games (unlike in Mass Effect 3).
Opening the Sandbox: After a certain event, you gain the ability to explore Ferelden and Orlais.
The Order: The Inquisition, an organization formed to restore order and root out conspiracy.
Order Reborn: The original Inquisition was disbanded nearly a thousand years ago.
Party in My Pocket: Party members disappear when the Inquisitor is mounted and re-appear when the Inquisitor dismounts.
Party of Representatives: The party members embody various viewpoints and have differing levels of investment in certain issues, as discussed here.
Playable Epilogue: You can continue to explore the world after you complete the main questline.
The Inquisition's headquarters, Skyhold, is a central area where the player can speak to their companions, similar to the party camp in Origins. The fortress is also customizable to some degree, similar to Admiral Anderson's apartment on the Citadel in ME3. The Inquisition gains other fortresses as the story progresses.
The Village of Haven serves as the Inquisition's temporary headquarters until the player gains control of Skyhold.
Player Party: As in the previous titles, you can switch control to any member of your current party at will.
Point-and-Click Map: Unlike in the previous games, you can travel quickly between known places even on the local map of the area, simply by selecting your destination—which is probably due to the sheer size of outdoor levels.
The Power of Friendship: Focus is a resource that is built up in combat through teamwork and allows the party to use powerful abilities such as slowing down time for their enemies.
Powerup Mount: You can now ride horses to get around areas faster.
Pre-Order Bonus: The Flames of the Inquisition DLC, which includes weapons, gear and an armoured horse.
Previous Player-Character Cameo: Hawke appears in the Enemy of Thedas trailer, helping the Inquisition fight a giant demonic spider. You will be able to customize Hawke's appearance and personality.
A Quest Giver Is You: As the Inquisitor, you can send rank-and-file agents of your organization on missions (presumably, the same agents and similar missions as seen in the Coop Multiplayer). This is in addition to Player Party members who also work for the Inquisition but instead fight alongside the Inquisitor in normal gameplay.
For party members, some pieces of their wardrobe always remain the same, like Cassandra's trenchcoat-like garments.
For the Inquisitor (and everyone else), a new crafting system allows you to produce replicas of equipment you already own from the materials (and thus colors) you prefer but with the same stats.
Relationship Values: The approval/disapproval system returns, however the approval bar is now invisible to the player. The player is not told how many points are added or removed from a companion's approval bar, only that a companion approved or disapproved of the player's actions.
Romance Sidequest: Various romance options for your main character are available, as in the previous games. Indeed, developers have confirmed eight love interests, more romance options than any previous Dragon Age game. From the beginning, Cassandra and Blackwall are straight, Iron Bull and Josephine are bisexual, Sera and Dorian are gay, and all six are available regardless of race. When the developers got extra time, Cullen was made romancable by female humans and elves, and Solas was made available to female elves.
Sequel Escalation: The inqusition will be building up forces like in Origins, but with Orlais thrown into the mix.
Shield-Bearing Mook: In the same vein as the Cerberus Guardians in ME3. This emphasizes party teamwork - you can't punch through the shields even with magic, so you need to flank or disarm them.
Shoddy Knockoff Product: In-Universe; Word of Godsays that "Hard in Hightown 2", the book next to Cassandra's maps, is an unauthorized sequel to Varric's original. The book had previously appeared in Varric's companion specific sidequest in Mark of the Assassin, where he was furious to discover someone ripping off his work, leading him to collect all the copies he could find at Chateau Haine so he could burn them.
Stopped Numbering Sequels: Originally announced as Dragon Age III: Inquisition, the III was eventually dropped from the title, due to the transition to next generation consoles. Plus, DAIIII as the abbreviation probably would have been awkward.
Swamps Are Evil: Ferelden gets a third evil swamp: the Fallow Mire was ravaged by a plague and the plague's victims have risen as undead.
Tarot Motifs: The party member selection screen consists of a deck of tarot cards modeled off of the party members. Each party member's card is based off of one of the major arcana.
The Limited Special Collector's Ultimate Edition includes an actual tarot deck as one of its contents, which will presumably use the same imagery and expand on it for the cards not already represented by the party members.
"Intricate mechanisms are the core of the artificerís craft: deadly traps; distracting contraptions; marvels of engineering turned to deadly purpose. If an artificer is standing at the far end of a seemingly innocuous stretch of the battlefield, you should find another path."
War for Fun and Profit: The Hidden Villain is deliberately prolonging the various wars for their own benefit. Case in point, the Breach opens right on top of a peace summit for the Mage-Templar War.
War Is Hell: Many characters are scarred by the events of the civil war. The first trailer shows the world on the verge of collapse, with a shell-shocked Varric standing amidst a field of dead in Crestwood.
The War Room: Skyhold has one, complete with war table. The war table allows you to manage the Inquisition's operations: side quests that you send your agents to take care of.
The War Sequence: One region is so thoroughly under enemy control that you have to send in your army to deal with it.