Unicorn Stump

Effects

Gives invulnerability and +0.28 speed for six seconds, but removes the ability to shoot tears while the effect is active.

The invulnerability effect negates all forms of damage, including health loss from Blood Donation Machines and Devil Beggars.
Does not prevent Red Heart container loss from Health Down pills or Devil Room deals.
The item is similar to My Little Unicorn, with faster recharge time at the cost of being unable to damage enemies while under its effects.
If another spacebar item is picked up while in the invulnerability state granted by Unicorn Stump, Isaac will return to normal immediately, becoming able to shoot tears and take damage.

???'s Only Friend: The fly can still be controlled while invincible.
Any touch-based attacks or status effects such as Aries or The Virus: Freely usable in every room.
Any orbital-like item ( Cube of Meat, Sacrificial Dagger): The orbital can be used freely in every single room, making it a great alternative source of damage.
(Added in Repentance) Book of Virtues: Spawns an orbital rainbow Wisp on each use of Unicorn Stump, giving up to 8 extra orbitals. Wisps do not deal contact damage.
- When Isaac is invulnerable, wisps become much more vibrant and deal contact damage equal to 2x Isaac's damage -5.
- If Isaac has less than 2.5 damage, the wisps will deal no damage even if Unicorn Stump is active.
Mom's Knife does contact damage in the same direction it was being held at the time of using the Unicorn Stump, giving a massive amount of free damage by ramming into an enemy.

The Ludovico Technique: The tear stays in place while Isaac is invincible; although Isaac cannot move the tear, it will continue to damage enemies during his invincibility. This is very useful for stationary enemies.
(Added in Afterbirth) Marked: Isaac's tears will still fire, but he will be unable to move the crosshair while invincible.