Particularly the Dungeons & Dragons alignment.
True neutrality is generally considered unfeasible, mostly because its philosophies have not been well-defined. For example, the concept that a druid can be true neutral is a strange one. Druids are most obviously aligned towards the benefit of their environment and their continued cause. Many see them as being the equivalent of a priest or paladin in their domain, but that they simply do not appreciate "loudness" from outside influences. In order to maintain general peace, they seek to create obvious balance in the forces around them. Each side would come to understand the futility of warring with the other.
D&D had a habit of forcing importance on alignment, and it shows with the concept of true neutrality. Many have taken another view of the true neutral alignment and say that it is more of a neutrality by inaction. They use it as an idea, not an ideal. For them, characters purporting to believe in neutrality tend to be neither selfless nor self-serving, aligned to no cause in particular, and tend to be with a party simply because the circumstances appear appropriate.
Generally speaking, a true neutral character will constantly be reaching for reasons to care about anything, and will be hopelessly lost within their own philosophies and goals.
Often times, this type of character is far too difficult or stressful to play properly, and a player will become stressed at the weight of the character persona.