+1 for TOML. If you think simplicity matters, look at the YAML spec [1], vomit and never use it again.

If you still don't believe me, try implementing a conforming YAML 1.2 parser (oh, and try not to make it a source of RCE [2]...).

[1] http://yaml.org/spec/1.2/spec.html

[2] http://blog.codeclimate.com/blog/2013/01/10/rails-remote-cod...