My JSON parser ( github.com/nanoscopic/ujsonin ) has these things:

0. Looks essentially the same as JSON

1. Core data types, and customizable data types can be added easily.

2. Arrays, Objects, and arbitrary nesting.

3. Comments ( both /* */ and // format )

4. Multiline strings ( by default; carriage returns are no problem within strings )

5. It is JSON with relaxed restrictions and slight addition for actual named types.

6. I've written C, Perl, and Golang implementations so far.