9 single-player games that got crazy multiplayer mods

Oh, you brought guests

Everything is better with friends--drinking, travelling, starting a cult, but mostly gaming. Of course, not every game is meant to be played with others. Titles like BioShock Infinite and Resident Evil 4 are great single-player experiences because they were designed that way.

But what happens when you take a game meant to be played alone and open up the Pandora's Box of multiplayer? Savvy game-modders create shared experiences in massive worlds like Skyrim, or entirely new game modes for strategy titles like Mount & Blade. Games like these didn't need multiplayer--they weren't meant to have it--but got it anyway, thanks to the mod community.

Just Cause 2

Just Cause 2 is a study in vehicular insanity--few games let you leap from a plane in mid-flight, pull out your grappling hook, and zip into the cockpit of a different plane. That grappling hook, in fact, leads to some of the most insane, nearly game-breaking moments you can have with Just Cause. You see, the grappling hook can attach to anything, letting you zip toward an object or attach two things together. This leads to pure chaos in single-player.

Now imagine what grappling hooks can do in the hands of dozens of other players. People hijack speedboats, attach cargo to planes as they take off, and chain their friends to moving vehicles--that's just part of what this multiplayer mod allows. Others get into vehicle races, but these quickly devolve into clusterfraks of people latching onto the jeep in front of them, while racers in jets above just crash into each other. It's basically Michael Bay's wet dream.

Torchlight 2

"It's like a single-player Diablo!" was the cry of many a Torchlight player when the original hit Steam in 2009. They were right--this randomly generated dungeon crawler lets you level a class, sling spells, and grind for sweet loot. It was everything Diablo-ites could want, but it only let them play alone.

Then came the Synergies mod. This takes everything good about Torchlight--dungeons, combat, and item drops--and opens it up for others. More than that, it totally overhauls the leveling, crafting, and dungeoneering systems, even adding high-level raids. This takes Torchlight 2 vanilla and blends it into an awesome Torchlight MMO frappuccino.

Oblivion and Skyrim

In Oblivion, you wake up as a political prisoner in a dank dungeon. In Skyrim, you ride a cart with other POWs to your execution. These are memorable openings of two of the best Elder Scrolls journeys, but the tales you create in the lands of Tamriel are for you alone--those other prisoners are nothing but NPCs.

Not so with Oblivion and Skyrim Online, two mods that are exactly what they sound like. These take dozens of your Cyrodiil- and Skyrim-bound heroes and throw them together in their respective games. Jumping through Oblivion gates and screaming Fus-Roh-Dah at dragons never feels as cool as with a party of fellow dragonborn. The best part? Both mods preempted Elder Scrolls Online--way to go, modders!

Fallout 3

Elder Scrolls isn't the only Bethesda series to get the multiplayer treatment. If you're more into post-apocalyptic sci-fi than wizardry, look no further than the Fallout 3 multiplayer mod. Remember that cancelled Fallout MMO? Looks like we didn't need it after all.

All the laser-blasting, perk-picking adventuring of the Wasteland can be played with others on dedicated servers. Even better, the mod is completely open to Fallout 3's DLC expansions and other user mods. It's the Fallout 3 you remember, coated in user chat and whatever craziness you decide to add to your journey. Now everyone can fight over the Naughty Nightwear.

Grand Theft Auto: San Andreas

Most of you will think of Grand Theft Auto 4 or 5 when it comes to Grand Theft-ing with friends. GTA 4 started the craze of vehicle races and death matches on Xbox Live, and GTA 5 took this to new heights with GTA online. But things actually got crazy much earlier with GTA: San Andreas. What's more shocking is that San Andreas polices itself.

As in, you literally play as police--the mod works like a giant game of cops and robbers. You can make arrests or be arrested, and any cop cars on your tail are driven by real-life players. It's an internet anomaly of gangs and police squads, all working with and against each other in San Andrean harmony.

Euro Truck Simulator 2

What's more fun than trucking precious cargo around Europe? You can shift and cruise through proud nations like France, Narnia, Poland, and the UK--one of those might not actually be real--in real-world big rigs. Do well enough, and you can even hire other drivers to do your business for you.

Oh, was none of that interesting to you? Then what about doing it all... with friends? Yes, with the Euro Truck Simulator 2 multiplayer mod, you and your driving buddies can haul the goods together Or, you know, just turn the thing into bumper cars and blast some Adele on your custom radio station.

Mount & Blade: Warband

For RPG buffs who would rather swing swords than sling spells, there's Mount & Blade: Warband, which forgoes all fantasy elements for a more authentic feel. It's action-oriented--you battle in fields, forests, and forts--and you spend a lot of time on horseback. Makes sense that the multiplayer mod would let you take on other players in full-on medieval warfare, right?

Wrong answer buzzer noise! That's what the regular game does! Warband's Full Invasion mod is actually a lot more like the horde modes of Gears of War and Halo 3: ODST. You and a buddy mount up, blade up, and survive as long as you can against waves of enemy knights. This mod was so popular, it warranted a Full Invasion 2 mod. Way to go, mounter-bladers!

Half Life 2

I know what you're thinking: "Everybody knows about this mod. It's just Counter-Strike!" Well, you just answered the Mount & Blade question wrong, and here's your second buzzer. This isn't Counter-Strike--it's GoldenEye.

That's right, this is a total conversion of the classic Half Life 2 into the equally beloved GoldenEye 64. The team behind the mod worked to recreate all the details of the Nintendo 64 title, and it looks even better on the Source engine. Modern advances like dedicated servers and party systems mean you don't have to gather everybody together on the couch to have a good ol' fashion 007 time. Slappers only, no Oddjob, no Gravity Gun.

The Legend of Zelda: Ocarina of Time

Let's stop for a moment. The previous mods on this list are all pretty nuts, and although we never asked for them, they're much appreciated. But this final mod--a hack, really--is easily the most mind blowing I've ever seen. Just look at it.

This is Ocarina of Time with four-player co-op and it runs on a brick-and-mortar Nintendo 64. At its core, it adds nothing to the game, but there's something undeniably amazing about watching four Links running around Kokiri Forest, working together to slash grass and break pots for rupees. It makes many a puzzle much easier to solve, too. Four Swords ain't got nothin' on this.

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These games were never meant to have multiplayer like this, but savvy players made it happen. Now, those crazy single-player moments can be shared with others. Do you support these sorts of game-changing mods? Do you think it's nothing more than cheap hacking? Let us know in the comments below.

Want to dig into some more mods? Check out these 8 hilariously ridiculous mods for games you know and love. If you're in the mood for more shooting with others, check out the best FPS games.