Games

I never played it but the Thomas the Train mod for skyrim is hilarious.

GB Mario 2 in full color

Tale of Two Wastelands for Fallout 3 and New Vegas.

Gregtech: New Horizons

Technically a modpack rather than a mod though. I love grinding through technological advancements.

promods for ETS 2 and ATS 2

Mekanism, hands down.

Followed VERY closely by Fallout 2 Restoration Project.

Sven-Coop for Half-Life 1.

I've played, almost daily, since the mod was released in January 1999. Over a quarter century. I've got admin in a number of servers, so a lot of days I'm just hopping on briefly to make sure the servers are running smoothly and no one is trolling. New maps are still being regularly released, many by people who have been mapping for it for a solid 15-20 years.

No idea of total hours. It wasn't added to Steam until 2016, but I have multiple thousands of hours logged since then. I've got to be over 10-12k hours since the beginning. Easily.

Everything else in my life has shifted. Sven-Coop is my rock.

Rimworld multiplayer.

I couldn't pick a single one, but I got endless joy from all the Quake mods back in the day. Not just level designs and sprite replacement, but complete weapon changes that made everything different, Quake Kart, Cujo, etc. It seemed the sky was the limit.

I don't know if time has been kind or not, but when I discovered Fall from Heaven II for Civilization VI I never launched the base game again.

I think I haven't played a single skirmish round of Company of Heroes 1 without the Blitzkrieg mod in the past 15 years.

Terraria - Calamity.

Expands the game to 2.5x the content.

Absolutely amazing, would recommend buying Terraria just to play it.

Garry’s Mod

It’s hard to think of any one mod that got remotely close to changing a game the way GMod did for HL2/CS:S/source engine titles. I spent thousands of hours in GMod as a kid, it added infinite teplaya ility to the HL2 campaign, forums like Facepunch and PHWOnline became my second home. There was a ton of content to be loaded from there and FPSBanana, the thriving webcomic scene was truly special.

Better Than Wolves it's a minecraft overhaul that was started by the veteran game designer FlowerChild who was pissed at Mojang that they are adding useless features that don't improve gameplay loop (wolves being the breaking point). So he spent many years making Minecraft challenging survival and interesting tech game.

While I haven't beaten the dragon once in that game (not many people have) it still gave me hundreds of hours of entertainment.

Gigastructural Engineering for Stellaris... the megastructures included in the game and DLC are great, but they lack a certain insanity. Plus the mod allows you to terraform any planet (even gas giants).

Enderal, a whole new game built ontop of Skyrim. Offers an entirely different setting, map, class system, enemies, spells, and has an actual story that you will not soon forget.

Sky UI. Not the same game without it.

I've never been one to mod games, I'm pretty vanilla when it comes to gaming. Play the base game and thats it. Rarely do i even try any dlc. With that said, I thoroughly enjoyed Frelancer discovery back in the day. It is a freelancer multilayer mod that brought a lot more content and enabled multi player once the official servers were gone.

Archolos, and it’s not even close. This is one of the best gaming experiences i’ve had in years

There are so many... I'll just go with a couple

Fallout 3 Wanderers Edition always comes to mind for making that game so much better to play and more stable than the base game. I wouldn't replay FO3 any other way

Elden Ring Seamless Co-op is what ER co-op should have been to begin with. God it's so good I put another couple hundred hours in to replay every inch of ER+DLC with a friend.

The mod that got me into modding still has a special place in my heart. It was the Shockwave mod for C&C Generals. Shockwave absolutely could have been vanilla if EA deigned to finish the Zero Hour expansion. It was just pure polished perfection for that game.

This was a tough one. But I'm probably going to have to say JSawyer Ultimate for Fallout: New Vegas. A continuation of the game director's own rebalance mod, it makes the game hard in a way that feels fresh and fair (unlike the baked-in Hardcore mode).

I like to pair it with my runner-up: JAM - Just Assorted Mods, for a more modern HUD and a sprint feature. Of course then you need the NPCs Sprint mod to rebalance combat and- you know what, all of the Viva New Vegas modlist while you're at it ;)

The Fallout London mod for Fallout 4 was incredible. It's like a an entire new game for free. They really captured the spirit of the Fallout universe. Better than anything Bethesda put out in the past couple years

There's a Sonic fan game I like to play called Sonic Robo Blast 2, built on an extremely heavily modified OG Doom engine with a pretty good modding community, and there's a level pack for it called Sol Sestancia that's just crazy fun to run through with the Neo Sonic character mod. Getting up to top speed to activate boost mode and trying your best not to slow down or stop so you don't lose it. So satisfying.

STALKER Anomaly with GAMMA on top of course.

I'm going to have to go with either the Create mod or Apotheosis, both for Minecraft. Both of them feel like they could just be part of the vanilla game, and at this point it feels wrong and weird for me to play the game without them installed.

I'd have to say thanks to SMAPI and Content Patcher for enabling so many Stardew Valley mods in the first place.

Also, Qwinn's Ultimate DAO Fixpack for allowing me to have a mostly bug-free experience playing Dragon Age: Origins. Mostly.

NEOTOKYO°

I haven't bothered with mods for years now but Neotokyo was by far my favourite. Apparently it's still played to this day by a group of fans but I haven't joined in. Also the soundtrack is amazing

Most impressive:

Assetto Corsa Custom Shaders Patch / Content Manager

Tiniest mod which solves biggest frustration:

Heroes of Hammerwatch rejoin mod

Hoi4 player-led peace conferences. Because the game is literally unplayable without it

P.S: I know this isn't the type of mod you meant, but often the small fixes are the most important

!Wicked Whims!<

Sekiro - For the sake of Ashina

Star Trek Armada 3 for Sins of a Solar Empire. Can't wait for STA4 for SoaSE2.