i havnt found any but...

[Gligar_Man]

are there any items that are non-benefficial to your pogeys, like poison them or whatever? i was wonderring because that would make that exchange move *forgets what its called* that exchanges held items... would be fun to use,

[Gengar's Dance]

I dont think so and you are looking for the move trick

[soggy_cardboard]

nah, the only nonbenefitial thing in the game is slaking's trait.

but u can steal the opponents berry, and switch it with an item that does nothing in battle (ex. potion)

[TeleFox]

If heard from quite a few reliable sources that there are berries that will heal some HP, but confuse the pokémon if it's personality means that it doesn't like that taste. Check out http://www.orpg.net/players/karbear/pkmn/berries.html for a list of what berries do what, and there's another site (somewhere out there) that actually tells you what personalities are effected by what berry.
I haven't had a chance to check it out myself, I'm not that far into the game (seeing as I actually waited for the real thing to come out ^-~), but I'd say it could be fun!
With random personalities, you've got a 1 in 5 chance of confusing the enemy, but you can improve your odds if you know your opponent, or can at least have a good guess at what kind of personality they have.
Combine the loss of their shiny item with confusion and you could really make someone's day! *s*******

[Anonymos]

Just steal their beneficial item and leave them with nothing. Only one pokemon needs an item for Trick to work, and, unlike Thief, it never fails to steal the other pokemons item(if any).

[VaporousPhoenix]

I wish thye had an item that Paralyzed your pokemon automatically. Yes, it would have uses other than Trick. It would make Facade an attack worth using. Double's attack, but auto paralyzes. Facade would 0wn many things then. I even thought of an item name, The Trump Card.

[Gligar_Man]

thx for your guys help.. i was pretty sure but not entirely... im just gonna attack a bike or something.. o_O lol