Item: Animal Crate (DK)
This item acts and has the same properties of the normal crate. However once it is thrown and breaks, a random Animal Buddy will come out. The Animal Buddies that can emerge and their effects are as follows:
Rambi - charges back and forth across the stage ramming into characters
Enguarde - lunges several times, easy to avoid but high damage if contact is made
Expresso - runs quickly back and forth across stage, doing multiple hits. Low damage but hard to avoid due to Expresso's speed
Winky - jumps on nearby characters when they take to the air, footstool jumping them back down. Must be in Winky's vicinity, but effective spiking
Squitter - shoots webbing a characters, immobolizing them momentarily and exposing them to follow-up attacks
Ellie - shoots water at characters, pushing them off the stage. Not as powerful as Kyogre, but moreso than the FLUDD.
The Animal Buddy disappears after several seconds. If you attack the crate and it breaks the Animal Buddy will target you instead of an opponent.
Item: Reeking Box (FE)
The user opens the box and summons a horde of Risen (3-6, for the sake of not having too many on screen). Once summoned they act pretty much like ReDeads did in Melee, but if they make contact with you (apart from your hitboxes), it's more like a Like Like, with the more Risen on you the harder it is to break free.
Item: Energy Tank (Metroid)
The user picks up the energy tank, and it is stored in their inventory, much like a dragoon part or that other one I forget the name of. Once the user hits 100%, they are automatically healed back to zero, and the energy tank disappears. If they pick it up at >100%, they heal 100%.
Item: Ultra Hand
The user picks up the Ultra Hand, which grants them extended grapple (even characters like Link and Samus), and gives them tether recovery as long as they are holding the item.
Item: Shield (Sonic)
The user is bestowed with a perpetual shield that does not minimize. It breaks after taking a cumulative 25%, or after an attack that deals more than 25%, but upon breaking it will not stun the character. It flashes red when it is about to break.
Item: Sheikah Slate (LoZ)
The user holds the Slate with both hands, operating it similarly to the Cracker Launcher. The targeted character will glow yellow, as Stasis is used on them. It has relatively close range and delay before the effect sets in, allowing the opponent to dodge. It is difficult to target moving opponents. However if successful, the opponent is immobilized for several seconds and damage can be done to them. Much like in BotW, all knockback done is cumulative, allowing for massive launching power.
Item: Inkzooka (Splatoon)
The user holds the Inkzooka with both hands, again like the Cracker Launcher. The Inkzooka can not be directed upwards, it only targets horizontally. The Inkzooka has six shots, with the traveling pillars of ink getting taller the further they go. The disappear when the reach the edge of the platform they were launched from. Opponents trapped in the pillars are carried with them.
Item: Oil Drum (DK)
Oil drums act like normal barrels. However when thrown and rolled, they leave a slick trail of oil. This can either trip opponents, or, if contact with fire is made, leave a firey trail which damages opponents before being extinguished several seconds later. If the barrel is attacked with fire without being rolled, it will light, much like in the picture. After several seconds on fire, it will explode, damaging all those nearby, including the user who lit it.
Item: Master Seal (FE)
The user holds the Master Seal and holds it aloft, like the Special Flag. If they remain uninterrupted for a few seconds, the Master Seal will glow and unleash its power, granting the user with notably enhanced speed, jumping, mobility, damage, knockback, and knockback resistance for 10 seconds. If the user is attacked before the Master Seal unleashes its power, they drop the item and an opponent may be able to steal it.
Item: Leaf (AC)
The user picks up the leaf like a normal item. However when it is thrown it changes into a random piece of furniture. The heavier the furniture piece, the more damage it does.
That's all I can think of atm.