Egoist: someone with a philosophical self-involvement amounting to egoism (who may or may not be an egotist, e.g. a person with the trait of selfishness).
Psychological egoism is the view that humans are always motivated by self-interest, even in what seem to be acts of altruism. It can be contrasted both with ethical egoism, which is the view that the individual always ought to be motivated by self-interest and disregard the interests of the community, and rational egoism, which asserts that the rational thing to do in all situations is that which furthers the actor's interests the most. Psychological egoism is controversial, since many see it as an over-simplified interpretation of behavior, and it cannot rule out altruism without being contradicted by evidence. Rather, it claims that when sane people choose to help others, it is because of the personal benefits they themselves obtain or expect to obtain, directly or indirectly, from doing so.