Blanket / Holy Card / Holy Mantle / Wooden Cross: if Metronome is used while the shield is active, any stat changes or familiars/orbitals generated from Metronome will persist between rooms until Metronome is used again or replaced with another active item. Items that modify your stats and have other additional effects will keep the stats but the effect will be gone after leaving the room. For example, the tears down applied from The Inner Eye will persist between rooms, but Isaac will not shoot three tears at once.
Some tear effects from items will remain active between rooms. These include:
Car Battery: Metronome is activated twice at once as expected, but the item chosen for the first activation is shown raised above Isaac's head, instead of the second one that actually remains active.
D8's rerolled stat multipliers will persist, D4 or D100 will reroll all items permamently and D Infinity mimicking any of the previous also has the same effects.
Void absorbing passives and granting stats will persist.
Limited and unusual effects include:
Items do not spawn pickups and consumables that they might when picked up normally.
Items that adjust Isaac's size will not do so.
1up! and Guppy's Collar give no indication of extra lives, but will still work if you die in the room.
Abaddon will not remove red hearts or grant black hearts.
Belly Button and Mom's Purse allow picking up two trinkets in the room, but if another one is picked up outside, one trinket disappears completely along the extra slot.
Black Candle only adds a black heart and does not remove curses.
Brittle Bones and Divorce Papers do not grant bone hearts. Brittle Bones can still be used to gain permanent tears ups if bone hearts are available.
Crown of Light only adds soul hearts, no damage multiplier.
Dead Cat will only restore one red heart without setting heart containers to 1. It also gives no extra lives.
PHD will not identify pills, but they are still guaranteed to not be negative.
Schoolbag allows picking up two activated items while in the room and they can be kept even outside, but the extra slot and one of the items is lost if another activated item is picked up.
The following items remain active until the Metronome is used again or replaced with another active item:
PC It is possible for this item to use an item that can teleport one to the I AM ERROR room. During the Mother Boss fight, this can happen. Using the trapdoor causes the game to crash.
Bug!
PC It is possible for this item to give an indefinite Breath of Life effect that persists throughout rooms, eventually killing the player.