Protagonists who lack traits commonly attributed to heroes, such as nobility, bravery, selflessness, etc. Generally any villainous and/or selfish protagonist though includes cowards, fools and others.
Name variations: selfish protagonist
The first video game about Anti-hero protagonist was released on March 14, 1983.
Although protagonist is often interchanged with main character and hero in various contexts, the last one is only because it's the most common type of protagonist. As such the name of this tag is not paradoxical by implying unheroic hero (negating itself), instead it stands for unheroic main character.
Can be combined with hero protagonist.