Technically, a kilogram is a unit of mass, not weight. Several items that have a mass of approximately 1 kilogram include a liter of water and a large dictionary.
The mass of a liter of water is very close to a kilogram. A liter of fresh water at 4 degrees Celsius has a mass 1.000028 times that of a kilogram.
Certain quantities of objects that individually have masses less than a kilogram can be combined together to make up a kilogram. For example, three cans of soup have a combined mass of approximately 1 kilogram. If one takes 15 C batteries, the combined mass of the batteries is approximately 1 kilogram.
The human brain has a mass slightly larger than 1 kilogram. Most adult brains have a mass between 1.3 and 1.4 kilograms.