A bag of brightly coloured construction bricks.

This has two possible uses, 

Create Item: The bricks connect together and can be used to create any one non-magical item that the user is familiar with, such as a key, a rope, a short sword or a standard potion bottle. Once constructed the item begins to glow, and transforms into a fully functional version of that item. The effect lasts for 1 minute and then the item returns to bricks.

Sharpened Terrain: When emptied on the ground, the bricks scatter creating difficult terrain covering a square of 10ft. This causes 2d6 piercing damage. On each subsequent round that any creature begins or ends it's turn within the effected area it takes 1d6 piercing damage.

This item has 3 charges before the bricks lose their magical power and become simply a child's plaything.