No love for Fallout: London?

It's not just a Fallout 4 mod—it's full-blown AAA experience—done so well that I'd believe it was made by the New Vegas devs if I didn't already know. If you're tired of waiting for Bethesda to make the next FO game, just play this instead.

Counter Strike and Team Fortress. Both were Half Life mods when they started.

Surprised no one has said MyHouse.wad yet

Black mesa. Half life and half life 2 modder community is amazing.

"The Last Days" for Mount & Blade. Intro

Mount & Blade was a medieval combat simulator where you're a wandering mercenary in a war torn region. The gameplay was somewhat innovative when it came out (originally 2008), but as far as story and setting, it was kinda meh. But the great thing about it were the mods, and by far the best mod was "The Last Days," a total conversion mod that lifted all the mechanics but put it in The Lord of the Rings.

These nerds put so much detail into that mod, it was incredible. I didn't know half the factions existed. The map goes beyond Gondor and Rohan and even Rivendell, it goes all the way out to the goblins of Mt. Gundabad fighting against the men of Dale. Each location has tons of detail, some of them are truly massive, and they pushed the limits of the base game with trolls and giant spiders and things like that. Each individual faction has their own faction strength, so you have to think strategically about where to reinforce. The differences between how each factions' units fight on the battlefield is more emphasized, and tbh the combat is a bit better balanced.

It really hit the nail on the head of what to do with the game engine, and then put real passion, creativity, and effort into making it work (seriously, the last update was in 2017, new stuff was being added after nearly a decade. And there's comments on the page I linked as recently as 10 days ago, so people are still playing it). Next to it, the base game feels a bit more like a proof of concept. The open world nature of the game really allows you to take in the setting and experience the story from a different perspective, rather than following the heroes from the books. It really made the setting come alive in a way I haven't found in really any other LotR game (although I'm not super into the setting and haven't played a ton of them).

The mod was for the original game at first but it update when they put out the sequel, Mount & Blade: Warband, so if anyone decides to check it out, get that one rather than the original.

Multiverse Mod for FTL

Its literally just a free sequel

It's lesser-known, but the Battletech Advanced 3062 mod for Battletech from Harebrained Schemes is incredible. It adds so much it's almost an entirely new game (but still Battletech).

I was always astounded by hl2 mods.

There was one in particular that I really liked but it always crashed on me when I got even a little far in it. You spawn in a hotel and have to get away from the combine or something. I don't remember what it was called. But I really liked the idea of it.

Entropy: Zero 2 For HL2 was awesome

RogueTech for battle tech is amazing. Hundreds of hours into it.

Otis_inf's camera tools. Blows away any in-game photo mode. No restrictions on movement at all, can pause or frame-advance the game, there's even a camera rails system I haven't fucked with yet.

I've never played it myself, but Gary's Mod was all the rage back in the day.

Multiplayer for GTA San Andreas was quite revolutionary at its time.

A Link to the Past/Super Metroid combo randomizer. Both games smooshed into a single ROM, with certain doors taking you from one to the other. Item pools are then shuffled together, sending you on a big scavenger hunt to find Metroid items in Hyrule so that you can explore Zebes to find Zelda items so that you can explore Hyrule.

Unfortunately it's somewhat lopsided due to how much bigger ALttP is than SM, but the technical novelty of it is amazing and worth a playthrough.

Space Exploration for Factorio. My dude built a huge mod for free, then was hired by the devs to desogn the paid sequel, Factorio 2, and although large and great its still smaller and less complex then the mod.

In terms of actual impact, a Fallout: New Vegas mod named Tale of Two Wastelands that takes a Fallout 3 copy and brings all of it into the Fallout: New Vegas world.

The mod makers didn't create the great bulk of the content, made a converter, but it amounts to a new experience with an AAA-game level of content addition.

Does make me wonder about other mods that can leverage pre-existing work. Cataclysm: Dark Days Ahead had a mod where someone imported a real life map of Massachusetts, for example. Some flight sims can do similar stuff.

Elden ring seamless coop. I can't believe that such a small file could create such a better experience in the game.

Since someone already mentioned Fallout London, then I'll recommend Shutoko Revival Project for Asseto Corsa, a full blown open map in the speedways of japan with online support and even functioning traffic so the illegal racing isn't a breeze.

Young me (and current me too) was always blown away by the Game Genie on the NES. Simple piece of tech that could do so much with so many games.

Strawberry jam for celeste. It's a huge collaborative project that introduces 100+ levels (base game has 25) with a really wide range of difficulties, graphical styles, new mechanics, original music and ideas on par with the quality from the base game. Definitely a must play if you like 2d platformers

Withers big naturals

Save Our Ship 2 for RimWorld basically turns the base game into a sequel of itself.

Tamriel Rebuilt for Morrowind is also pretty dope and it isn't even finished yet.

Dragon Genitals for Monster Hunter World. Gave each monster either a realistic cloaca or an incredibly well-crafted dong, tailored to the individual style of each monster. The details were amazing, like a monster called Bagel Goose has a rock dick, but when he transforms into B-52 bomber mode he glows red hot with lava… and his cock does, too.

Are Skyrim mods allowed, or is that cheating? 😜