Apple!

Effects

The chance to fire a razor blade depends on the luck stat. The activation rate is equal to 1/(15 - Luck). At base luck (0), the chance is 6.66%, maxing out at 100% at 14 luck.

Cricket's Body / Compound Fracture / The Parasite: When razors are fired, the split tears will also be razors and do quadruple damage. The Parasite's split tears look like normal tears.
Dr. Fetus: Adds a chance for the bombs to deal increased damage. See the page for the specific damage formula.
(Removed in Repentance) Glass Cannon: Adds a chance to fire a giant razor that does roughly triple damage.
- (Added in Repentance) Adds a chance to fire a giant razor that does quadruple damage (x40 + 10 flat damage).
Haemolacria: Adds a chance for tears to do quadruple damage. Burst tears will also do quadruple damage if the main tear does quadruple damage.
Technology Zero: When razors are fired, they will connect to other tears via electricity. The electricity also does quadruple damage.
Lachryphagy: Tears can be fed to razors, increasing damage and splitting into 8 razors after a little while. If razors are fed to the tears, the razor damage doesn't apply to the tear both before and after splitting.

Brimstone: Each entire beam has a chance to gain the damage boost.
- (Added in Repentance) Each tick of the beam has a chance to gain the damage boost.
Tech X: Overrides Apple!.
- (Added in Repentance) Each tick of the laser rings have a chance to gain the damage boost.
Tough Love: With 14 luck, overrides Tough Love, as the razor blades do more damage anyways. With 13 luck, Apple and Tough Love each have about an equal chance to trigger.