YAGS is another game system. It is a set of moderately complex tabletop RPG rules designed around the concept of cinematic realism, allowing gritty adventures where the life of a hero is a dangerous one.
YAGS is flexible. It can be used with a wide range of settings, genres and playing styles, from fantasy to science fiction, from real world to supernatural horror.
YAGS is free. It can be modified and distributed under the terms of the GPL, for both commercial and non-commercial purposes. If you want to tweak the rules and use them in your own games, then the source is available to allow you to change it and print your own PDFs.
Rules at a glance: Point buy character generation system, skill based with no classes or levels. All skill checks are attribute x skill + 1d20 against a target difficulty. Attributes are commonly on a scale of 3-5, skills on a scale of 0-8.
First play tested in 1995, YAGS was designed as a simple, modular set of rules for low fantasy games. Today, the core rules have grown in complexity and now assume a semi-realistic modern setting.
Additional modules provide rules for creating characters in both historical and hard science fiction settings. YAGS core rules are the same for any setting, and characters are compatible across settings, but the way characters are generated and the options they have available to them can change between settings and genres, providing a compromise between setting flavour and consistency.
YAGS aims for a moderate amount of crunch - rules designed to provide detail to characters and actions rather than assuming players will simply roleplay correctly. For example, it uses an advantages/disadvantages system and relatively detailed skills to allow characters to differentiate themselves.
However, implementation aims to keep this within a core set of simple rules. The playing style of YAGS tends towards Cinematic Realism - skilled characters can be awesome, but aren't super heroes. You will still need to dodge bullets and swords, but if you have the right skills and abilities, at least you will be able to dodge.