Adds a chance to shoot red fist-shaped tears that deal extreme knockback and cause confusion for 2 seconds.
Enemies will take 10 + 2 * (floor - 1) damage when they are knocked into a wall/obstacle or when hit by another knocked back enemy.
Notes
The chance to fire fist tears depends on the luck stat, and the formula used to determine the chance is:
At base luck (0), the chance is 10%, maxing out at 100% at 8.01 luck.
Bosses are also affected by all of Knockout Drops' effects.
Fist tears play a unique punch sound effect when they hit enemies.
Knockout Drops can be dangerous in The Beast battle, as the Ultra Harbingers may get knocked so far off the screen they become hard to damage further and their attacks cannot be seen properly.
Synergies
Aquarius: The trail of tears has a chance to knockback enemies.
Knockout Drops is from the Antibirth mod. In Antibirth, enemies would not take extra damage from being knocked into something else but still deal damage to enemies they are knocked into.
Taking this item as Keeper will give him the expression of Bum-Bo the Brave, and by extension, Bumbino.
Gallery
Keeper's unique appearance with Knockout Drops, resembling Bum-Bo the Brave and Bumbino.
The Beast battle, as the Ultra Harbingers may get knocked so far off the screen they become hard to damage further and their attacks cannot be seen properly.
Aquarius: The trail of tears has a chance to knockback enemies.
Brimstone: Gives the lasers high knockback.
Jacob's Ladder: Enemies that are shocked by a knockback tear will also be knocked back.
The Ludovico Technique: Hovering tear alternates between a normal tear and a fist.
Technology: Laser receives knockback effect as with normal tears.
Spindown Dice: Turns into 
R Key when rerolled, allowing the possibility of multiple R Key uses in a single run.
Keeper will give him the expression of Bum-Bo the Brave, and by extension, 
Bumbino.
The Binding of Isaac: Rebirth
