Your best item

[Pokemonsean]

What item best helped you in in Battle
Item and Pokemon holding that item

[bobandbill]

Moving to the polls section.

I suppose Leftovers often has helped, and money wise Amulet coin is invaluable (hurr).

[carboncopy]

lucky egg helps a lot in traning

[Furret-Luver]

i always, always, always use the exp share. it helps a lot with training, especially when you first hatch an egg an the pokemon is to weak to battle.

[Shadow♠]

Lucky Egg for the Exp.

[Mystical Jackal]

What item best helped you in in Battle
Item and Pokemon holding that item

You should reformulate your question. In-game battles? Frontier battles? Linked battles? Some members above suggested items that would be useless in frontier battles, like Lucky Egg and Exp. Share, for example. And though in in-game battles some items wouldn't help the Pokemon during battle (Amulet Coin, for example, it helps the trainer gain some cash, it doesn't alter the performance of the Pokemon that holds it, therefore it doesn't help you in (during) the battle).

Considering in-game battles I would use Lucky Egg in the first story. In the pos-story I would prefer Amulet Coin. This because level wasn't going to be that a problem if I have already reached Elite Four and can battle against them again ilimited times.

If it were a frontier/linked battle, I would always use Leftovers on a high HP Pokemon, and the rest of my items were going to hold stat uppers, which will varies from a moveset to other. Leftovers and stat uppers have always been the best for me.

[The Sandslasher]

When I was younger I played Emerald and had a screwed up Sandshrew, it lost all of its attacks because they were replaced by defense moves over time. Then I got cut for it and it actually started winning battles.

[wobbanut]

The best items to use or have pokemon hold IMO are smoke balls and the 4th gen berries like yache, chilan, and rindo. Smoke balls let you escape from everything in the wild, and the 4th gen berries help lessen the power of super-effective moves against your pokemon. The status-curing berries of the 3rd gen like cheri and pecha were nice, but I like the 4th gen ones much better because they give your pokemon a chance of lasting longer in a battle if you're surprised with a supereffective move you didn't know your opponent had, or if your pokemon is the last one standing against a type it's weak against.

[Excitable Boy]

Revival Herbs, X anything.

[Dragonicwari]

I've already stated this today, but every item has its uses and there is no best item. Some can be more useful than others but all has some sort of niche