Item Name: Berserk Gene
Old Effect: On switch-in, raises the user's attack by 2 stages but confuses them. Single use.
New Effect: If the holder is hit by a super effective move, its attack, special attack and speed rise by 1 stage.
Flavor: Kinda similar to weakness policy but trades power for speed. Slower pokemons will usually prefer berserk gene while faster ones will use weakness policy.
Item Name: Absorb Bulb
Old Effect: Raises holder's Sp. Atk by 1 stage if hit by a Water-type attack. Single use.
New Effect: Raises holder's Sp.Atk by 1 stage if hit by a Water-type attack. Grants Water immunity. Single use.
Item Name: Cell Battery
Old Effect: Raises holder's attack by 1 stage if hit by an electric type attack. Single use.
New Effect: Raises holder's attack by 1 stage if hit by an electric type attack. Grants Electric immunity. Single use.
Flavor: An immunity can be very helpful. The problem with Cell Battery and Absorb Bulb is that they give boosts when hit with an attack of a certain type but they're not reliable or worth using over other stat boosting items like the choiced items and the stat boosting berries. This simple buff of making the user immune to a certain type makes them more similar to air ballon which is an item that sees somewhat common play. I think this buff would make absorb bulb and cell battery see a lot more play.
Item Name: Muscle Band
Old Effect: Holder's physical attack have 1.1x power.
New Effect: Holder's physical attack have 1.3x power but its speed is halved.
Item Name: Wise Glasses
Old Effect: Holder's special attack have 1.1x power
New Effect: Holder's special attack have 1.3x power but its speed is halved.
Flavor: Another duo of items. New Muscle Band and Wise Glasses are gonna be very good on Trick Room teams or on pokemons that don't care much about their speed such as Swords Dance Rillaboom, Bisharp or Scizor.
Item Name: Slippery Sled
Item Effect: Increases holder's speed by 50% under hail and makes them immune to hail damage.
Flavor: This could make hail viable because every pokemon has access to that 50% boost from hail thanks to that item while other weathers only give the speed boost to pokemons with a specific ability.