This mod works with the Farewell to Arms update.

This is a WIP compilation of unused and cut content (does not add a custom floor) that was fixed and reintegrated into the game.

Welcome to the Synergy and Balance Update. To see the restored items (no new one added) please scroll a bit down.

Synergies:

• Hidden Tech Shotgun: Flipping a table now shoots the projectiles of the Big Shotgun.
  • Table Tech Shotgun + Big Shotgun
• College Ball: Nanomachines' effect triggers more often and after triggering it you deal double damage for a short amount of time.
  • Nanomachines + Ballot
• The Great War: The M1 also makes you invisible when you reload from an empty magazine.
  • M1 + Grey Mauser
• Double Chest Friends: The chance of Ring Of Chest Friendship to give you a chest as a room reward is increased by a further 25%.
  • Ring Of Chest Friendship + Ring of Mimic Friendship
• Galaxy Defender: When Sunglasses' effect triggers, Grasschopper instantly reloads and fires a projectile with increased size and damage.
  • Grasschopper + Sunglasses
• The Star War: Fully emptying either gun's magazine immediately switches to its fully reloaded partner gun.
  • Void Marshal + The Emperor
• Kingpin: Hitting enemies at least 3 times with one shot from Serious Cannon recovers 1 ammo when it dissipates.
  • Serious Cannon + Turkey
• Gunship Sinker: RC Rocket's rockets gain increased size and damage the further they travel.
  • RC Rocket + Combined Rifle
• Precious Metals: Killing an enemy spawns 1-5 extra Shells in addition to the enemy's other loot.
  • Gold Junk + Platinum Bullets (this synergy does not apply to synergy chests)
• Shard Blade: Sprun has an additional random trigger, doubling the chances of turning into Windgunner.
  • Sprun + Excaliber
• High Energy: If an enemy is killed by the Combined Rifle's energy ball, it release a burst of The Fat Line's shots upon dissipating.
  • Combined Rifle + The Fat Line
• Riot Gear: Damage dealt to the police officer is reduced by 50%.
  • Badge + M1911 or Colt 1851 or SAA or Cold 45 (basically any Colt¹)
• Irradiated Ones: The chance to shoot poison bullets is significantly increased.
  • Irradiated Lead + Uranium Ammolet
• Grasscutter: While holding Alien Engine, Grasschopper orbits you. When you dodge a bullet it fires a free shot at the nearest enemy.
  • Alien Engine + Grasschopper
• Trashkan: Ser Junkan's attacks also poison enemies hit.
  • Ser Junkan + Trashcannon
• Heart Unlocket: Grants an empty heart container.
  • Heart Locket + Shelleton Key
• 20/20 Tears: Changes Tear Jerker into a special form (synergy with Directional Pad has priority).
  • Tear Jerker + Sunglasses
• Double Moon 7: Changes Moonscraper into a special form.
  • Moonscraper + AU Gun or Klobbe
• Fruits and Vegetables: Changes Banana into a special form.
  • Banana + Broccoli

¹ This was my own choice as the original gun was removed from the game and the 'To Serve Android' synergy is also easy to get and is an upgrade.

Synergies containing starter items:

These synergies don't apply to synergy chests and you can use the console to enable / disable them (saved over multiple launches, remember to use Tab for autocomplete):
cuttingRoomFloor StarterSynergiesEnabled (default: true)

• Hell Singing: The Crossbow deals 50% bonus damage against jammed enemies, stacking with Silver Bullets, for a total of 487.5% damage dealt.²
  • Crossbow + Silver Bullets
• Husky: Additionally spawns two small pup versions of the two canine companions (just visual).
  • Dog + Wolf
• Open Bar: Molotov Launcher now launches a volley of three molotovs. While holding it, using the Molotov restores 5 ammo to it.
  • Molotov Launcher + Molotov
• Reinforced Lockpicks: Trusty Lockpicks turn golden, increasing their unlock chance from 50% to 100%.
  • Trusty Lockpicks + Master of Unlocking
• Look, No Hands: Allows to dual wield both of Robot's hands.
  • Robot's Left Hand + Robot's Right Hand
• Supply Drop Update: Spawns two additional supply crates containing random room rewards.
  • Supply Drop + Galactic Medal of Valor
• Chickensword: Blasphemy is still able to fire its sword projectile even when you are not at full health (or are the Robot).
  • Chicken Flute + Blasphemy
• Easy Enough: Dodge rolling now reloads 6 bullets to the Dart Gun instead of one (I know this is very similar to the 'Reload Roll' synergy).
  • Dart Gun + Easy Reload Bullets
• Harmless Fun: Both guns deal 25% increased damage.
  • Dart Gun + Mega Douser
• Recessive Hero: Number Two's effects now also apply when not alone.
  • Number Two + Ancient Hero's Bandana

² Let me know if you want this to work for all crossbows.

Other synergy changes:

• The 'Like Shooting Fish' synergy now once again includes the 38 Special, M1911 and Derringer as optional guns instead of only the Backup Gun.
• The 'Diazepam' synergy now once again applies to Crestfaller, Laser Lotus, Shock Rifle, Thunderclap and the Crossbow (does not include the Crossbow if starter synergies are disabled).
• The 'Battery Powered' synergy now includes Battery Bullets as an optional item and also includes the old 100% projectile speed effect for the Shock Rifle from the old unnamed 'Battery Bullets + Shock Rifle' synergy (if starter synergies are enabled).
• The 'Hacker' synergy (Lower Case r + Bracket Key) now gives the Lower Case r its intended alternate form in addition to the 25% damage increase (alternates with Upper Case R depending on which synergy was last picked up).

Balance changes:

• Katana Dash
  • completely removed the movement lockout delay at the end
  • significantly reduced range to improve usability
  • briefly at the end of the dash, bullets around you are destroyed (like Bloodied Scarf)
  • damage now scales per floor
  • now adds 1 curse
• Thunderbolt
  • the bonus damage for shrunken targets now also applies to bosses and is now listed in the description
  • reduced cooldown
• Thirst For Vengeance
  • now additionally grants 5% rate of fire per missing half a heart (or per armor missing from 6 armor for the Robot if at less than 6)
• Old Journal
  • doubled chance to trigger and added a sound effect when it triggers
• Table Tech Hole and Table Tech Mirror are now also a part of the 'Paperwork' synergy (thanks to Hotklou for the suggestion)
• Changed a few item qualities

Current Items:

• Katana Dash: Dash into a direction turning invisible and invincible. At the end of the dash damage everything that was in the path. Can be used up to three times each room.
  
• Thirst For Vengeance: Increased rate of fire the closer you are to defeat. You enter a bleedout state on death for a short time. If you kill an enemy during the bleedout state you revive and heal for a small amount.
  
• Hungry Caterpillar: Companion that follows you around and eats heart pickups. Once it has eaten 2 full hearts transforms into Fairy Wings.
  
• Fairy Wings: Grants flight. Rolling leaves pink slime that temporarily charms enemies (only accessible via Hungry Caterpillar).
  
• Cue Bullets: Enemies are launched backwards on death, and deal damage to other enemies they hit.
  
• Old Journal: Clearing a room without taking damage increases the chance for a room reward (same effect as the bugged Hunter's Journal).
  
• Monster Ball: Captures an enemy and spawns it as a permanently charmed follower upon release (made with Apache Thunder).
  
• Table Tech Hole: Flipping a table creates a black hole for a short duration.
  
• Table Tech Mirror: Flipped tables reflect bullets back at the enemy (based on an unused sprite).
  
• Brittle Bullets: Increased damage, but you lose all ammo for the current gun when getting hit (based on this).
  
• Bubble Shield: You deflect bullets for a few seconds. Recharges once every two rooms cleared.
  
• Thunderbolt: Shrinks and dazes enemies for a brief period of time, increasing damage dealt to them.
  

Item IDs: If you want to spawn the item use 'give gr:X' where X is the item name in lower case and with underscores instead of spaces (Remember to use autocomplete). Fairy Wings are an exception, as they were already accessible with the mtg console, so the ID is simply 'fairy_wings'.

If you have any balance or feature suggestions let me know.

Installation
Get MTG:

• Download Mod the Gungeon at: http://modthegungeon.eu/#download
  
• Make sure Enter the Gungeon is closed
  
• Open ETGMod.Installer.exe and press "Step 3: Install ETGMod"
  
• Close dat thang
  

Installing mods:

• Go to your Enter the Gungeon Steam directory, usually located at:
  "C:\Program Files (x86)\Steam\steamapps\common\Enter the Gungeon\"
  
• If there is not one already, create a folder called "Mods"
  
• Drag CuttingRoomFloor.zip into the Mods folder
  
• If there is a "mods.txt" file in the Mods folder, delete it
  
• The directory should look like this: "Enter The Gungeon/Mods/CuttingRoomFloor.zip"
  

Then launch the game. If Mod the Gungeon installed correctly, you can press F1 to see the list of active mods. 

Open the console with ~ or / or F2 to enter commands.
Type help for a list of commands and remember to use Tab for autocomplete.
Source Code: https://github.com/Goldenrevolver/Enter-The-Gungeon-Mods/ .