Since I can not edit the previous list that can be found here S&Box Gamemode List (Outdated), here is a new and better list that will stay up to date and it will be a wiki so all of you can post updates. 
This list contains all gamemodes that hopefully you will see once S&box is released.
If you want to check out some gamemode samples, the best place for that is #waywo channel on S&box discord.
Other topics that are worth checking out:
Gamemode List
Links will direct you to either forum topic or gamemode page.
- marks a gamemode from devs that have S&box access, some will direct you to GitHub repo.
Made by Facepunch
Remakes
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Prophunt
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TTT Reborn for S&Box
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Death Run by Gvarados
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Team Fortress 2: Redux
- Making Jailbreak For S&Box (Gamemode)
- Cinema Gamemode
RP
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Gamemode: YourRP (Global RP Gamemode)
- CivitasRP - A realistic roleplay framework for S&box
- RP-Base: roleplay framework for all RP needs
- Space Station Lambda
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S&rp - unique roleplay gamemode
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CWRP - Star Wars Roleplay in S&box
- Liver Failure
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Minge RP
RPG
- RPG Project Zero (previously RPG/MMO Gamemode )
RTS
FPS
- S&Box/Source 2: Doom Horizons Multiplayer
- Ultimate Survivor, a fast-paced & fun Gamemode
- Shooter: Revived
- Slambox - my S&box gamemode
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Element - A hero based arena shooter made for S&box
PvP
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gKarts - Kart racing & more in s&box
- Tinyships - The ship building, tiny pirate battling gamemode
- Baby Tennis - Smack babies across the map!
- Larry’s Rumble
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MultiTanks
- Variant: A reverse survive & escape game
- Source & Swords
- Shitters - The first and greatest shitting gamemode
- Space Rising - Planetary Conquest
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Bounty
- Gamemode: Ragdoll Royale
- Mushroom Bomber - A Fresh spin on the Bomberman games inside s&box
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PolyStrike
- OvO - The one versus one gamemode for when MW2 Rust just ain’t gonna cut it
- Alex’s Instagib
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Heist
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Downmatch
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Quake 3 style DM98
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Naval - The S&box Sucessor to Naval Play
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s&boxing - 1v1 Fighting Gamemode
Forts
- Fort Wars
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Battle Builders - PVP Base Defence
PvE
- Guerillaz Gamemode
- Chloride: The High-Octane Hovercraft Shooter
- Tower Defense
- Neon Ninjas - a Fast-Paced PvE Roguelike
Survival
- PostNukeRP 2
- There Was Hope - A brutal survival experience
- DayZ S&Box Gamemode Concept
- Panic in the Facility - Where the stress take place
Zombie
Platform & Speedrun
- Dine’N Dash gamemode
- Ascension - A Game mode where you climb up stairs for hours with friends!
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Strafe - A speedrun gamemode based around strafe movement mechanics.
Other
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Frankly Fishing: A fishing adventure gamemode for s&box
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Sportsbar
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Aperture Studies - Hot Loading Centered Game Dev Tutorial Series inside S&box
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Minigolf
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Hide 'n Seek
- Puzzle Community / Gamemode
- Burger Speed (fast food game concept)
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Ballon Party
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SledBuild
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Minigame Party
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DVD
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Sauna
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Space Rocks
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Fornite Building Prototype
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Run Away
