Items can be found all across The Binding of Issac Rebirth, for example and item room or curse room, etc. The come in such varieties as passive items or spacebar items. Plenty more could be in Rebirth but it isn't out yet. Consumables are not included here, instead they're on the Consumables page.
Spacebar Items Edit
Spacebar Items are items which must be activated, usually have to recharge and for the most part last only a single room. There are plenty exceptions to these rules.
The Jar Edit
The Jar is a spacebar item bought exclusively from the Shop, for an unspecified amount of money. It allows Issac to store extra hearts in it for use later. It can hold 4 Full Hearts and is emptied through activation.
Tammy's Head Edit
Confirmed to be in the game, Tammy's Head has a one room recharge. It allows Issac to fire large tears in Eight directions, tear modifiers apply so you could fire 8 Homing Brimstone Mom's Knives.
Passive Items Edit
Passive Items are items which have an effect which is always there. Some effect tears or stats, etc.
Champion Belt Edit
Mom's Perfume Edit
Presumably acting as a mom item, Mom's Perfume it increases Issac's tear firing rate as well as adding a 15% chance for Issac's tears to induce fear, which for those unaware causes enemies to flee.
Tiny Planet Edit
The Tiny Planet causes tears to orbit around Issac. It also serves as a double range upgrade.
Pheremones cause enemies to walk towards one another rather than chasing Issac.