I like json

I kind of wish it had two and only two features: defined ordering, and comments

As to languages for configuration (specifically), I wish there was a good specification for a program config, where you would have one well-defined configuration file for defaults, and a user-specified configuration file for the values you have set/overriden.

say default.config:

  {"player_name":"player", "mouse_speed":5}

and my.config:

  {"player_name":"me"}

in some way that upgrading the program could do stuff with default.config without destroying your existing config.