Borderlands 3 Challenge Run Modifiers

Manufacturer Allegiance = You can only equip a single manufacturer for your weapons, shield, and grenades.
Defenseless = You can't equip any shields (with the exception of the Rough Rider).
Gun Allegiance = You can only equip a single gun type.
Swapper = Every time an item drops you have to equip it and replace your current equipment.
Favorite Color = You can only equip one rarity color.
Actionless = You can't use your action skill.
Anti-aim = You can't aim down sights.
Lost Backpack = You must drop your entire backpack and can't store anything else in your backpack.
Empty Magazine = Once you start firing, you must keep firing until your magazine is empty.
Bigger is Better = You have to equip items with the most damage/highest shield capacity and must use the weapon with the most damage.
Reincarnation = When you die, you have to drop all of your equipped items.
Empty Wallet = You can't spend money on anything.
War of the Uniques = You can only equip uniques or legendaries.
Windy Day = Once downed, you must bleed out. Second winds aren't allowed but you may stay alive for your FFYL duration.
My Favorite Gun = You can only have one gun equipped at a time.
FPS Loadout = You can only have one primary weapon equipped (SMG, Assault Rifle, or Sniper) and one secondary weapon equipped (Heavy, Shotgun, or Pistol).
Immersion Mode = You can only do story quests.
Elementalist = You can only equip gear with elemental stats, anointments, or resistances.
Elemental Allegiance = You can only equip a single element damage type (ignoring shields).
Bigger isn't Better = You have to equip items with the lowest damage/lowest shield capacity and must use the weapon with the least damage.
Embargo = You can't use shops (including ammo refill).
Broken Legs = Once you're in combat and first take damage, you are not allowed to move until combat ends.