Gambit Pileup: Not even counting side groups like the Orc tribes and Shadow thieves, the main plot has at minimum five major factions, two and most of a third of which have been wiped out by the player and each other by the time you actually have any kind of handle on what's really going on.
Game Mod: Like the previous game, NWN2 comes with a toolkit for building new modules and even entire campaigns. They run the gamut from lousy and cliched to really damn good (rivaling or surpassing the official releases in a few cases). A good source is Neverwinter Vault.
Gameplay and Story Segregation: Cleric Player Characters of any deity can freely choose Domains. A Law-aligned god wouldn't allow the Chaos Domain and vice versa. And no evil god in the game (except Luthic) allow healing. Hell, there are no gods in the game that allows both default Domains, Sun and Healing. Lathander is the only one having Sun and he didn't allow Healing in 3.5e.
Genre Savvy: Used and lampshaded in the same sequence if the player was Genre Savvy — just before the end, Garius will notice if the protagonist previously removed all gear from the characters who joined him, noting "Nice try, but ultimately futile" before giving them equipment.
This also happens if they're still carrying all of their original equipment by the game's end.
Amie, Bevil and Kipp, but most prominently various NPCs involved in escort quests.
Also, Shandra Jerro.
Hard-Coded Hostility: Can be either played straight or averted, due to the advanced faction building system available to module builders. A faction can be made hostile, indifferent or friendly toward any and all other factions, including the "player" faction, independently as required.
Hate Sink: The King of Shadows is a dangerous threat to Neverwinter and indeed the Sword Coast at large, but once you learn his sad, sad backstory, he becomes a tragic figure who inspires pity rather than hatred. The githyanki get little individual focus and it's hard to hate them all as a group. Although she puts the Ass in Ambassador and is smug and abrasive during your trial, Torio Claven can become more helpful and less unpleasant once you defeat Garius if you recruit her for Crossroad Keep, and pulls off a genuine Heel–Face Turn in the epilogue if you do. But Black Garius? He treats his underlings like dirt, works for the King of Shadows and plots to usurp him with no Freudian Excuse or long-term justification. And after he becomes a Shadow Reaver, he starts mind raping Neeshka and tries to corrupt your True Companions over to the side of Evil. Killing him is thus immensely satisfying.
Heroes Want Redheads: The only romanceable female companion, the druidess Elanee, with auburn hair. In addition, two other early companions who aren't romanceable: the half-demon rogue, Neeshka, and the ginger sorceress, Qara. If the player starts the game with a redheaded close-combat character, it's possible to create a well balanced party of four redheads.
Neeshka arguably still counts when it comes to romance, seeing as how she was planned to be romanceable during development.
Grobnar: No one really knows how big the Wendersnaven are. They could be thousands of Khelgars high! Khelgar Ironfist: What did I say 'bout usin' me as a unit of measurement?! Grobnar: Er, right, several Neeshkas high.
Hostage for MacGuffin: The githyanki commanders do this using Shandra as the hostage, but only after Bishop tracks them back to their hideout and you hack your way through most of their troops. Then Zeeaire discovers that you've got another one of the Plot Coupons embedded in your chest and they abandon the attempt.
A lesser example as the Infinity+1 Sword pales in comparison to some player-made items in terms of damage and is useless to half the classes, although its special powers and useful stat boosts may help arcane spellcasters.
Inn Security: Usually the Sunken Flagon is pretty safe, given that it's frequented by adventurers and off-duty guards. The exception is when the githyanki attack and take Shandra Hostage for a MacGuffin.
In the first area you visit outside of your Doomed Hometown — the road to some seemingly-unimportant swamp ruins — the minimap reads "The Mere of Dead Men". Now, the player character knows the apt name of the creepy swamp their home village is built on, but the player isn't supposed to know that yet. Also, one of the initially greyed-out prestige classes is Neverwinter Nine, potentially spoiling the offer Lord Nasher makes to you much later in the game.
Also, since the developers didn't bother/weren't able to make it possible to change the names of NPCs on-the-fly and weren't willing to outright lie to the player, you can tell that someone's going to try and deceive you about their identity if the overhead label that appears when you mouse over them says something vague, like "Man", instead of their actual name.
Similar to above, while walking through town, you can cursor over various NPCs. Citizen, Citizen, Citizen, Thug ... gee, I wonder which of these will try to ambush me as I walk past...
Mask of the Betrayer and certain fan modules prove that it is in fact possible to script a character name change (the MotB instance being Kaelyn the Dove adding a similar Animal Moniker to your name), so we can probably put this one down to Obsidian not caring enough.
Similarly, you are told to rescue an envoy but that his name is unknown... however his name shows up in your Journal straight away.
It's Up to You: Sometimes it seems the player is the only member of the City Watch who is actually ever assigned any tasks of significance. This is because the guy giving your orders assumes most of the other watchmen are corrupt and doesn't trust anyone but you. The situation is about as good as it sounds.
Jerkass: Ribsmasher. You can set him free to have him thin out the ogre horde for you, but he also takes his anger out on treasure chests, breaking the contents. It's very tempting later on when you have a chance to get him electrocuted by having him try to open a certain door.
Justified Tutorial: The Harvest Festival explains all the basics and is entirely skippable.
Hoo boy, Johcris. The guy is willing to betray his own city to its worst enemy in order to kill Qara, just because she insulted his daughter. If you are cavalier enough, you can make his attitude seem more justified.
Also potentially Sand. Sure, Qara's not safe, and on her current path would no doubt turn out to be a major problem for anyone who crosses her. On the other hand, that's a pretty weak excuse to side with the Omnicidal Maniac in the process of corrupting and despoiling the world around you.
If you win the trial, Torio forces it to end in a trial by combat, same as you can if you lose. Khelgar then goes into an epic rant about how unfair this is and how pointless the trial was. The high priest of Tyr, god of justice, is actually so impressed by this rant that it gives Khelgar a major leg up in his quest to join the church as a monk later.
The name of the "Blessed of Waukeen" feat. Waukeen is the goddess of money and wealth. You paid an extra $10 to get this feat, and it's calling you a rich bastard.
The Silver Sword of Gith, an Ancestral Weapon of the githyanki and githzerai forged by Zerthimon for Gith to free them from the mind flayers. In the backstory it was lost in the Nine Hells, then recovered by Ammon Jerro to fight the King of Shadows, during which battle it was shattered. Its shards act as Plot Coupons to allow the blade to be reforged.
Another legendary weapon from the first campaign is the Hammer of Ironfist, the Ancestral Weapon of your companion Khelgar's clan. Unfortunately by the time you get it Khelgar is likely well on his way to becoming a Tyrran monk, meaning he relies on Good Old Fisticuffs instead of weapons, and the Hammer can thus only be reliably wielded by a dwarf player character. Or by Khelgar if you advise him not to become a monk after all after completing his quest, which is mechanically probably the better choice anyway.
Limited Special Collector's Ultimate Edition: First there was the Special Edition, which added the aforementioned "Blessed of Waukeen" feat to the Knight-Captain. It gave access to a couple of special shops, as well as a minor bonus on some dice rolls. Then there was the Gold Edition, which bundled the Special Edition with Mask of the Betrayer. After Storm of Zehir came out, they added it to the Gold box and created the Platinum Edition; it is this version that is available on Steam.
Lizard Folk: One of the monster races you encounter throughout the game. They sometimes serve as enemies for the player to overcome, but unlike other most monster races in the game they are portrayed sympathetically and can be reasoned with.
Logic Bomb: Subverted in the final boss battle. The Knight-Captain can try to pull this on the King of Shadows by pointing out that its overarching purpose, protecting Illefarn, is no longer applicable since said realm no longer exists. The King has extended the definition of Illefarn to include its descendants.
Loophole Abuse: The charges Luskan makes against you can mean that as a non-noble the treaty demands you will be sent to there for trial. If you followed the City Watch path, Nasher makes you a squire on the spot explicitly to exploit this, and justifying it with your service to the city. If you followed the thieves they just bribe a knight to take you on.