Jeremy Bentham Classical Utilitarianism
Humanity is governed by pain and pleasure. The principle of utility is that which approves/ disapproves of actions according to their augmentation or diminishment of happiness. Pain/pleasure are measured by their intensity, duration, certainty, frequency, fecundity (measure of pain/pleasure as juxt. to the first), and purity; only if the sum of these produces more pleasure than pain should the action be taken.
John Stuart Mill Utilitarianism Refined

Emphasizes the importance of quality over quantity in regards to pleasure. The only ones fit to judge if a particular pleasure is worth a particular pain are the experienced.

William Ross Intuitionism
Posits that we inherently know right from wrong, but this knowledge is not in every case self-evident. There are certain duties that we naturally assume and those are: fidelity, reparation, gratitude, justice, beneficence, self-improvement, and non-maleficence. Non-maleficence is more important than beneficence, and that fidelity, reparation, and gratitude are, in general, more important than beneficence as well.
Immanuel Kant The Moral Law
Ethics are absolute and its duties are categorical. Ethics are based on reason, not emotion. The Good life is a virtue, regardless if it requires sacrifice of pleasure or not. The only moral action to be taken is that which should become universal law.
Garret Hardin The Tragedy of the Commons
"The morality of an act is a function of the state of the system at the time it is performed."
The optimum population is less than the maximum because the planet and its resources are limited. The tragedy of the commons is the depletion of shared resources i.e., water, land etc., by individuals each acting in their own immediate self-interest but contradictory to the collective long-term interest. Hardin comes to the conclusion that appealing to the conscience is largely ineffective and the only effective action is the recognition of the necessity to legislate temperance of breeding through a form of penalties delivered via taxation.
Karl Marx
Each person should contribute according to their ability and receive according to their need.
"Communism abolishes...all religion and all morality, rather than constituting them on a new basis."
Jesus Sermon on the Mount
Do not judge, but love. Love your enemies as yourself. Be modestly pious for piety's sake; do not do it to be lauded by others. Do not worry, but trust in God and he will provide.
Nietzsche Beyond Good and Evil
The noble or