I assume this is a Metagame question, but I'm probably misinformed. xD
Brightpowder and Soul Dew are banned from the current OU/Uber Metagame, as far as I know, and just Brightpowder for NU/UU.
For Little Cup, only Berry Juice and Deepseatooth are banned.
Also remember that some trainers enforce the "Item Clause," meaning no two Pokemon can have the same item.