Returning stl containers from functions

What is the best way (performance-wise) of returning stl containers from a function? The container returned would usually contain several thousands of items.

Method 1:

typedef std::list<Item> ItemContainer;

ItemContainer CreateManyItems() {
    ItemContainer result;

    // fill the 'result' ...

    return result;
}

ItemContainer a = CreateManyItems();

Method 2:

void CreateManyItems(ItemContainer &output) {
    ItemContainer result;

    // fill the 'result' ...

    output.swap(result);
} 

ItemContainer a;
CreateManyItems(a);

Method 3:

void std::auto_ptr<ItemContainer> CreateManyItems() {
    std::auto_ptr<ItemContainer> result(new ItemContainer);

    // fill the 'result' ...

    return result;
}

std::auto_ptr<ItemContainer> a = CreateManyItems();

Or is there any better way?