The ammo mods
Put an ammo mod on a gun at the Arsenal machine for 500 salvage. Each one gives your bullets a chance to set off its effect.

DEAD WIRE
UNLOCKED FROM THE START · 500 SALVAGE
Bullets deal electric damage. Each bullet has a chance to stun a normal or special enemy, causing them to generate an electric damage field.

CRYO FREEZE
UNLOCKS AT LEVEL 12 · 500 SALVAGE
Bullets deal frost damage. Each bullet has a chance to slow a normal or special enemy and increase the damage they receive. Uses Thunder Wall until a frost ammo mod exists.
FIREWORKS
UNLOCKS AT LEVEL 18 · 500 SALVAGE
Each bullet that hits a Normal or Special Enemy has a chance to launch fireworks that target enemies.

NAPALM BURST
UNLOCKS AT LEVEL 35 · 500 SALVAGE
Bullets deal fire damage. Each bullet has a chance to apply a burn on normal and special enemies, dealing damage over time.

BRAIN ROT
UNLOCKS AT LEVEL 51 · 500 SALVAGE
Bullets deal toxic damage. Each bullet has a chance to temporarily turn a normal or special enemy into an ally.
Ammo mod augments
Dead Wire, Napalm Burst and Brain Rot each have 8 augments. See Augments.