Last-Second Karma Choice

The Last-Second Karma Choice is a type of Golden Snitch that occurs near the climax of a Video Game, where a single choice made by the player ultimately determines their placement on the game's Karma Meter. It may also lead to Multiple Endings.

Considering that a Karma Meter is generally intended to track and rate the player's progress throughout the game as a whole, this can result in awkward moments where a character who has spent the game playing to one side of the spectrum makes one choice that causes the world to regard them as the opposite -- especially if Evil Makes You Ugly, and the cackling horned protagonist is now the world's mightiest saviour.This also means that the player does not need to go trough the game again with a different character of a different alignment, just make a save before the important choice and they'll be able to see all the endings, killing off one of the strengths of replay value.

Compare One Judge to Rule Them All.

Action Adventure

 * In Famous. As the recipient of electricity-based superpowers, Cole has to choose whether to use them to help others, or help himself. Like all Karma Meter games listed here, your final karma, as well as the ending received, are determined by a specific choice just before the final boss. There's an interesting spin on it, though; the story event involved in taking the evil choice can leave absolutely no doubt about Cole's malevolence. Even if you make this choice with full positive karma, the karma meter locks.
 * Inverted in the sequel, where your karma actually limits what the final choice you make is. You have to be Good to take the good choice, and same for evil.
 * Deus Ex and Deus Ex Invisible War both have the ending you receive determined by a choice about halfway through the final level. It's Egregious in Invisible War as the entire game gives you multiple choices to side with multiple factions, but at the very end the faction you join and ending you receive is determined by a 3-option pull-down menu at the Daedalus Hub at the very end of the game (granted, your earlier actions in the game determine which factions are shooting at you and which ones are non-hostile in the final level prior to reaching the Hub).
 * Partially averted in Deus Ex at least, in that the three endings don't correspond directly to "good" or "bad" or to one side or other, so you're not negating any earlier choices. Although, the lead designer has said that he was trying to invoke this effect deliberately, because he didn't want players to be locked into a particular ending based on choices they made ten hours previously.
 * Deus Ex: Human Revolution subverts this. The four possible endings are available no matter what choices you've made throughout the game, but the tone of the endings depends on how you've acted the entire game. If you slaughter everyone in your path, then Adam's narration will be detached and robotic, indicating he's abandoned his humanity, and he'll essentially state that Humans Are Bastards and it's in our nature to destroy ourselves. Take them out non-lethally, and he'll be mostly hopeful, mentioning that he resisted abusing his power, and held onto his humanity despite losing (the vast majority of) his 'human' body; and he'll express optimism that humanity as a whole can do the same and make the right decisions for their own future. If you kill a moderate amount of people, Adam will be neutral, painting himself -- and humanity -- as a moral question mark.
 * The Nameless Mod also falls into this trope, but introduces more complexity. It essentially splits into two distinct storylines right at the beginning, but the choice on which of your current storyline's endings you get is determined at the very end. Thus, your choice in the beginning isn't invalidated at all. However, there's also a chance to Take a Third Option toward the end.

First Person Shooter

 * In Singularity, the ending you get depends on who you shoot in the final scene. You get your choice of ending depending on if you shoot one man, the other man, or both men.

Role-Playing Game

 * In the original Knights of the Old Republic, regardless of your Karma Meter, your final side is chosen in one action right near the end of the game, as is rather typical for SW games. (KotOR II does better at this, as it is based on if you kill the Jedi Masters, which is a major plot choice in each area. It's still possible to be "light" on the karma meter and go for the dark side ending, but much more unlikely.)
 * If you play a Dark Side character all the way through the game to reach the very base of the meter, go through the vital conversation mostly dark side but make the ONE vital light-side choice that pushes you up into low neutral, you can get back into deep Dark Side during the endgame and still get the Light ending with a pale, evil-looking character... not to mention Bastila apparently coming back from the dead, despite being killed in the Star Forge for DS points. Likewise, you can play through the whole game on the Light Side, make the one Dark Side choice, and get the Dark Side ending as a Happyshiny Jedi.
 * Of course, your Karma Meter determines how well you can use various Force powers —- if you build your character around using Light Side abilities and then suddenly turn to the Dark at the end of the game, you'll probably find yourself with a rather less powerful Sith Lord than if you'd been evil from the get-go.
 * In Jade Empire, your final alignment (and ending) is determined based on.
 * The final choice in Fallout 3's Broken Steel expansion basically sets your karma meter to one of two karma extremes . Not that it matters much, since the game is effectively over the moment you do, but it can net you some otherwise difficult achievements with relative ease if you Save Scum.
 * The DLC increased the level cap to 30, and in doing so introduced three perks that allow you to instantly change your karma to Neutral, Very Good, or Very Evil. This is the preferred way to get those pesky "Get to level 30 with  Karma" achievements, since the check occurs only after choosing your perks.
 * Baldur's Gate 2 has the Trials in the final dungeon, where taking even a single selfish choice instantly makes you Neutral Evil. This has no effect on your reputation, however, but changes your ending in Throne of Bhaal if you play that one.
 * Notably subverted in the first Mass Effect game, which looks like it's going this way when you're presented with the choice to However, while your choice contributes a boatload of points to one side or the other, the ending scene still depends on your overall Paragon/Renegade scores, and the dialogue will change accordingly.
 * Strange Journey gives you a choice of three paths shortly after beginning the final level, unless your Karma is very skewed towards either Law or Chaos, in which case you're simply locked into that ending.
 * Fable I does this as well; however, there is an evil character/good choice ending and a good character/evil choice ending in addition to the normal good and evil endings.
 * And let's not forget Fable II. You can choose one of three options: The good/evil bonuses are so massive that they can pull a complete 180 on any choice you made prior, and ultimately you're left with no middle ground or moral ambiguity. If you wanted to be neutral, well, at least you can pick the good end and go kill some peasants for balance.
 * Inverted by the tutorial implemented in the "Going Rogue" release of City of Heroes/City of Villains -- a moral choice made almost immediately upon starting to play determined whether your character is a hero or villain, and thus the entire course of the rest of the game.
 * Similarly, characters beginning in Praetoria had several opportunities to make moral choices which directed their careers as either government agents or revolutionaries (or both!), and finally had to choose to be a hero or a villain when given the chance to cross dimensions to Primal Earth.
 * This trope was also averted overall in gameplay -- while characters could change their alignments from hero to villain and back again (or vice versa), it required deliberate effort and was far from instantaneous.

Survival Horror

 * Silent Hill 3 has a karma/ending meter, and one event near the end can give a massive amount of negative karma. nets you enough negative karma to push you into the Bad Ending unless you are squeaky clean.
 * In Silent Hill Homecoming, the two choices that determine what ending you get both occur towards the end of the game, although there is an hour or two of gameplay between them and the final fight. Interestingly, one of the choices is identical to the one presented in Silent Hill 3, except the game considers the "good" choice to be the exact opposite one:.

Unsorted/Other

 * In Star Wars: The Force Unleashed, the final room of the game contains two bosses. Which one you choose to fight determines whether you get the light or dark ending.
 * The sequel doesn't even go that far. There is one final boss, and the choice you make after defeating him determines your ending.
 * Keeping with the Star Wars theme, while it's actually a few levels before the finale, none of your behaviors prior to in Jedi Academy make a lick of difference.
 * The first Jedi Knight is one of the few exceptions, as the ending-deciding choice is made automatically based on karma.