Dead Onion

Effects

Although the description says "Toxic aura tears", the tears do not do toxic/poison damage.
Using Dead Onion in a Crawl Space will cause tears to fall through the floor.

(Added in Afterbirth) Incubus: Does not affect shot speed or tear size, but still gives the piercing effect.
- (Added in Repentance): Shot speed, range, and tear size will be affected.

(Azazel) Azazel: Not recommended. Range penalty is the only effect.
Dr. Fetus: Not recommended. Bombs are slow to fire and will pass through enemies, making it far more difficult to hit them with explosions.
Epic Fetus: Overrides Dead Onion, although stat effects apply.
Brimstone: Overrides Dead Onion, although stat effects apply.
The Ludovico Technique: Not recommended. Tear moves very slowly making it hard to kill mobile enemies.
Mom's Knife: Overrides Dead Onion.
Monstro's Lung: Fires a barrage of large tears that disappear at close range. Spectral and piercing effects make it very effective at close range.
My Reflection: Not recommended. Tears will travel a very short distance before they return to Isaac and eventually disappear.
Proptosis: Not recommended. While tears do massive damage at short range, it makes it a lot easier to be damaged by explosive enemies or enemies that do contact damage.
Rubber Cement: Edges of tears retain both piercing and spectral effects; however, the center of the tear will lose them and bounce.
(Added in Afterbirth †) Sulfuric Acid: Not recommended. Acid Tears no longer impact objects and can no longer open Secret Rooms.
- (Added in Repentance) Acid Tears can break objects (but still can't open doors or Secret Rooms).
(Added in Repentance) Technology: Laser size is increased.