Obsidian Entertainment

In the year 2003, following long-standing disagreements with Black Isle Studios (Icewind Dale, Fallout, Planescape: Torment), its parent company Interplay laid off most of its staff. Most of the former Black Isle developers, including its founder Feargus Urquhart and writer/designer Chris Avellone, moved on to found a new game development company: Obsidian Entertainment.

Since then, Obsidian has formed strangely fond relations with fellow RPG company BioWare, to the point that its first two titles were sequels to BioWare games using modified versions of the originals' Aurora engine. This happened because by that point BioWare switched from producing licensed games based on established franchises (Neverwinter Nights and Knights of the Old Republic) to their own original universes, and in case of KOTOR, recommended Obsidian to LucasArts as an alternate developer for the sequel.

So far, Obsidian's games have been a mixed bag: deep and thought-provoking storylines on the level of the former Black Isle titles... and very buggy programming, usually requiring several patches to rectify(Or in some cases, fan-created mods.) though most games are fairly bugless with the final patch installed. This earned them the nickname "Bugsidian".

One thing to note about Obsidian is their business model. Obsidian is hired by publishers for fixed amounts of money, rather than being an internal studio or making a game then looking for a publisher to publish it. This results in Obsidian not bearing the finical cost or gain of the failure/success of any game they make beyond reputation or future deals. This mercenary model is responsible for their buggy reputation, as the release schedule or budget is not as negotiable once the deal is made. This came back to bite them in the ass with Fallout: New Vegas; their contract with Bethesda Softworks specified a tiered bonus based upon the game's Metacritic score. They missed the bonus by one point, which a more polished game almost certainly would have picked up.

Games released by Obsidian:

Star Wars: Knights Of The OldRepublic II: The Sith Lords
Neverwinter Nights 2 (plus expansions: Mask of the Betrayer, Storm of Zehir, but not the DLC Mysteries of Westgate)
Alpha Protocol
Fallout: New Vegas
Dungeon Siege 3
South Park: The Stick of Truth
Pillars of Eternity
Pillars of Eternity II: Deadfire
The Outer Worlds

Contributed to

Wasteland 2 (in co-operation with InXile Entertainment)

Obsidian Entertainment provides examples of the following tropes:

Anti-Villain: Many of their villains, though not all of them, are portrayed sympathetically even as its clearly laid out why they must be stopped. This includes Kreia from Knights Of The Old Republic II, Ammon Jerro (depending on your perspective) in Neverwinter Nights 2, Akachi (posthumously) in Mask of the Betrayer, and Benny in Fallout: New Vegas.
Author Avatar: Chris Avellone has admitted he often used Kreia to point out things that bugged him about the Star Wars universe. The same has been said for Ulysses of the Fallout setting.
The Artifact: The "influence" system used in most of their games was part of the Exile's special bonding ability in The Sith Lords. The system still works without the story connection though.
Black Humor
But Thou Must!: Alpha Protocol in particular was an attempt to subvert this. Obsidian has actually discussed this trope in a panel titled "But Thou Must" after the original trope namer, which got to the point where they made a drinking game of the word "Choice".
Corrupt Corporate Executive: The entire management team of Czerka Corporation, Leland in Alpha Protocol, and Mr. House in Fallout: New Vegas.
Darker and Grittier: Most of their games (except perhaps Alpha Protocol as it isn't a sequel to anything) can be considered this. This is most notable in Knights Of The Old Republic II, which is not only much darker and grittier than its predecessor but also than the majority of the Star Wars Expanded Universe (and that's saying something). One possible exception that is a sequel is Storm of Zehir, which is essentially a Lighter and Fluffier version of Neverwinter Nights 2.
- Considering the release period of The Sith Lords, one could make the argument that the darkness thrust upon the Expanded Universe was a byproduct of the game. The New Jedi Order series had recently finished, leaving the books on a high note. Much of the novels that have come out since have become increasingly darker and more depressing.
Dark Is Not Evil: Even Star Wars-based Knights Of The Old Republic II has elements of this, alongside Light Is Not Good.
Deadpan Snarker: One of Obsidian's favored dialogue models.
Deconstruction
Dialogue Tree
Evil Is Petty: Obsidian is often credited with averting or outright inverting this trope, whereas moral options in many RPGs play this straight. An exception is Neverwinter Nights 2, which is usually seen as playing this trope all too straight comparatively.
Game Breaking Bug: Sadly, this is pretty much universal in the initial release of a game, though in many cases these bugs are patched later on after development. Neverwinter Nights 2, for instance, arguably one of their worst games so far as this is concerned, is, as of the most recent patch, pretty stable.
Gameplay and Story Integration: In Knights Of The Old Republic II, your ability to influence your companions and swing their alignment is explained via an uncommon Force ability. In Neverwinter Nights 2, the reason monsters are constantly after you and the way in which you progress as a character is explained via a MacGuffin. In Mask of the Betrayer, a specific game mechanic plays an important role in the story. In Fallout: New Vegas, you have the option of playing the so-called "Hardcore Mode," which incorporates your need to eat, drink, and sleep into game mechanics as well as the fact that certain statistics can lead to other options in dialogue.
Gray and Grey Morality: The exact grayness of a particular game's morality is variable, but generally Obsidian stays pretty close to this trope. Villains will usually have sympathetic or at least understandable motives and goals, heroes are frequently ruthless or given to vices or pettiness, and moral choices are sometimes pretty ambiguous. There are usually a few exceptions that are clear Black and White morality within a game, but the tone as a whole is this.
Guile Hero: Obsidian does its best to allow you to play one if you so choose. Alpha Protocol, its only standalone game, and Fallout: New Vegas (which is part of a franchise that it effectively started) play this the straightest, allowing you to complete near-perfect Pacifist Runs and solve almost every problem through stealth or diplomacy as well as force.
Heroic Comedic Sociopath: Steven Heck in Alpha Protocol.
Hide Your Gays: Obsidian has been accused of this due to the lack of homosexuality in the majority of their titles (though they have a low number of heterosexual options due to the above mentioned dislike of Romance Sidquest). However, Fallout: New Vegas averts this trope completely, with one of the party members a Invisible to Gaydar Lipstick Lesbian and prostitutes in New Vegas servicing both sexes equally.
- New Vegas also allowed player characters to be homosexual or bisexual via specific perks. Similarly, a male Invisible to Gaydar doctor and a Lipstick Lesbian Brotherhood Scribe are available as party members, but their sexual orientations are only revealed in certain dialogue options.
- It's also noteworthy that Obsidian originally intended for Gannayev-of-Dreams from Mask Of The Betrayer to originally exist as a Gay Option for male player characters. However, WotC was evidently not amused and Gann was left as a purely heterosexual romance. Similarly, LucasArts was not interested in a Gay Option in either Knights of the Old Republic game.
Joisey: Project New Jersey (AKA "Seven Dwarfs", a fantasy game using Unreal Engine 3) was canceled.
Karma Meter: Present in every Obsidan game except for Alpha Protocol but it's actually very rarely used in a way that matters. Instead, Obsidian seems to much prefer the various variations of its "influence" meter, a mechanic that is omnipresent in their games and codified by them and which often fulfills a similar purpose story-wise that the Karma Meter does in other RPGs.
- Tellingly, Alpha Protocol is their only standalone game so far, and isn't burdened with a legacy Karma Meter from the setting or prior games in the series.
Light Is Not Good: Present in many of their games but played surprisingly straight in The Sith Lords, which is set in the often black and white Star Wars universe.
Optional Sexual Encounter: Notable in that Fallout: New Vegas, the only Obsidian RPG besides Storm of Zehir to not have a romance, plays this trope straightest.
Relationship Values: Obsidian's most significant contribution to RPG design is probably bringing these back into fashion.
Romance Sidequest: Present in most Obsidian games but the company as a whole appears uncomfortable with this trope and outright avert it in Fallout: New Vegas. JE Sawyer (lead designer of said game) in particular has been quoted as having a rather derisive opinion of the subject.
- That said, Sawyer and Chris Avellone also said a romance was planned for New Vegas involving Cass where she and the Courier would get hammered and wake up in Vegas married by The King, but was scrapped due to time.
Shout-Out
Sliding Scale of Idealism Versus Cynicism: Pretty much all their games lean towards or are knee-deep in the latter.
Sliding Scale of Linearity Versus Openness: All over the map, although there's been a general trend over time towards the latter. Knights Of The Old Republic II, Mask of the Betrayer, and Alpha Protocol are Type IV, Neverwinter Nights 2 is somewhere between Type III and Type IV, and both Storm of Zehir and Fallout: New Vegas are between Type V and Type VI, leaning toward the latter.
Tall, Dark and Snarky: Atton in Knights Of The Old Republic II, Sand in Neverwinter Nights 2, and potentially you in any of their games.
Talking the Monster to Death: An option in most of their games.
Teeth-Clenched Teamwork
The Man Behind the Man
Video Game Caring Potential/Video Game Cruelty Potential: A key element of Obsidian's "influence" game mechanic.
Where Are They Now? Epilogue: Continuing their traditions as Black Isle, Obsidian likes doing a closing narration detailing what the choices you made during the game eventually entail for your companions and locations you visited on your journeys.