Rotten Tomato

Effects

Adds a chance to fire tears that mark enemies. Marked enemies will be attacked by other enemies either until it is killed or it kills all the enemies attacking it (similar to the Charmed effect).
The tears, and hence the marked enemies, will change colour to red.
Marked enemies will also have their movement speed reduced.

The chance to fire marking tears depends on the luck stat. The activation rate is equal to 1/(6 - Luck). At base luck (0), the chance is 16.67%, maxing out at 100% at 4.01 luck.
Causes pathing issues with segmented bosses, as they attempt to attack their own segments.
Most enemies will ignore Isaac in order to attack a marked enemy, making Rotten Tomato an item with both offensive and defensive applications.
With a high enough luck stat and piercing effects, the up time of the marked effect can be enough to render some bosses harmless, such as Ultra Pestilence or The Duke of Flies who spawn a multitude of flies that it will then focus on.
This item is very effective during Boss Rush. Boss enemies affected by this item will deal massive amounts of damage to each other and Isaac will be less likely to get hurt by their attacks.