YAOSC (Yet Another Old School Clone)
Quirks are little special rules that do not fit easily into another of YAOSC’s systems. This includes tiny or rare situational advantages or disadvantages, abilities that do not call for an entire separate skill or mechanic, and the results of character “backstory” or role-playing. Some quirks are automatically gained by choosing a particular species or class; others may be chosen during character creation; others are gained during the course of play as the YAM feels appropriate.
Species and class abilities (low-light vision, dark vision, etc.)
Situation reaction modifiers
Siege engine use