Some characters, such as the Hunter, can absorb various forms of matter, which allows him to take on the properties of that form of matter. For example, if he absorbs water, then he will take on the form of water.
Characters such as Parasite, can absorb super powers from other metahumans simply by touching them. He can also drain them of their life energy. Other characters are able to absorb energy, and then direct it as an energy based attack, like Energy Projection, therefore it could be considered a more limited form of Energy Manipulation.
Absorbing the sun's energy is the key to Superman's powers. When he is in a solar system with a yellow sun, he absorbs it's energy, gaining his abilities, but when he is in a solar system with a red sun, he absorbs the energy, but it takes his powers away instead.