Here are some of the notable items:
RUGGED HELMET: adds the ability, "Rough Skin" to the holder.
BALLOON: Adds the ability, "Levitate" to a Pokemon until it gets hit by an attack.
RECHARGABLE BATTERY: While the holder holds this, any Electric-type attack it gets hit with will allow it to have its Attack stat raised.
ELEMENTAL JEWELS: Similar to the plates in D/P/Pt, except it's a one-time use item. Kinda crappy, but they're pretty common to find.
BULL'S EYE: Negates the opponent's immunities.
BULB: If held, the holder, when hit by a Water-type attack, will have its Special Attack raised.
These are the popular notable ones. Maybe people will name off more.