Warhammer FRP
Warhammer Fantasy Roleplay originally used a linear five placing system: Law - Good - Neutral - Evil - Chaotic. In changes of alignment (for whatever reason) a character moved one place along to the next position - so for example a neutral character could move to good or evil but not to chaotic.
In practice the system was used to regulate reactions between characters of different alignments.
In the newer edition, the concept of alignment (as well as, apparently, the presence of 'Law' as the antithesis of Chaos) has been discarded, with the emphasis more on the personalities and unique natures of characters, rather than a linear alignment system.
Read more about this topic: Alignment (role-playing Games)