Just a little reminder - any item that "can only be used once" can be restored with Recycle. I presume that Recycle can also replace an item discarded through Fling or Natural Gift. As for Knock Off, a Pokemon hit with Knock Off is still considered to have its held item, but said held item will not have any effect for the remainder of the battle (even if that Pokemon is switched out and switched back in.)
I actually have an item idea of my own. It would have been fine in Generation IV, but in Generation V... I'm not so sure...
Novacoda Berry: If the Pokemon holding this item is KO'd, it is automatically revived with 1/4 of its Max HP. The user is still forced to switch out unless it is the last Pokemon remaining on its owner's team, and a new Pokemon is brought onto the field to replace it at the end of the round as normal. This item can also be used from the bag outside of or during a battle to revive a Pokemon with 1/4 of its Max HP (sort of like a Revive with half efficacy.) Like any other Berry, it disappears once used. This Berry is compatible with Natural Gift, and provides an 80 BP Mystic-type attack. If Flung at another Pokemon, it heals that Pokemon for 1/4 of its maximum HP (no Base Power.) This Item can be stolen by Bug Bite or Pluck (which will result in the user of those moves immediately consuming it), and can also be destroyed by Incinerate. If consumed by another Pokemon by using Bug Bite or Pluck, it restores 1/4 of the Bug Bite/Pluck-using Pokemon's HP.
I think you can see why I have reservations about this item. In Generation IV, the only way to use it more than once would be Recycle, which would use up a precious moveslot (not to mention that it might be difficult to find the time to use it, especially since your Pokemon is at only 1/4 of its max HP and could very well be just KO'd again immediately after using Recycle.) But come Generation V, and we now have the Harvest ability, which automatically restores a used-up Berry at the end of the round! Granted, it doesn't have a 100% success rate outside of sunny weather, but still! Exeggutor and Tropius would become near-freakin' invincible!!! The only ways to get around a Novacoda Berry-holding, Harvest-using Exeggutor or Tropius [in sunlight] would be to hit them with Knock Off, Thief, Covet, Trick, Switcheroo, Incinerate, Bug Bite, or Pluck, or trick them into using a contact move on a Pokemon with Pickpocket (and Thief, Covet, and Pickpocket would require the user to not have an item!) And of those moves, Trick and Knock Off are the only ones to see significant competitive usage!!!
The purpose of this item is to give a Pokemon something of a safety cushion against knockout blows. Seeing as it only works once (except for on Pokemon with Harvest, gorramn it!), it's not exactly an insurmountable obstacle for the opponent, but it can still allow a Pokemon - especially a frail one - to get a second chance at victory. It can also help a Pokemon utilize a suicidal move more than once. Speaking of suicidal moves, the clause about the user being required to switch out in spite of having been revived is to avoid game-crashing awkwardness due to Healing Wish or Lunar Dance.
