Demon Weapons like Soul Eater Evans are able to reap and consume the souls of others to gain power.
Summary
Soul Manipulation is the ability to interact with one's soul or the souls of others. This ability ranges from being able to project the power of one's soul outward, grasping and ripping the souls of others out of their bodies, outright consuming souls to gain power, among other applications.
It should be noted that the ability to interact with souls and other non-corporeal entities directly as if they were physical objects is usually considered Non-Physical Interaction and does not grant the user the ability to manipulate souls in other contexts.
Under normal circumstances, most characters are assumed to have a soul by default unless the original medium specifies otherwise. Those who do not possess are soul are usually considered to be immune to most applications of Soul Manipulation.