I prefer C99. A smattering of features I like:
* Variable Length Arrays
* Variadic Macros
* Designated Initializers
* Anonymous Structs
* Compound Literals
* No built-in runtime or GC
* A choice of dynamic vs static compilation
* A good libc is wonderful but not necessary to get work done fast
* The tooling is mature and plentiful
1. Variable Length Arrays: Go has slices 2. Anonymous Structs: Go has these 3. No built-in runtime (in C): This is not true unless you are compiling -ffreestanding -nostdlib, etc. I have done this in C, but such programs have to call system-calls directly and provide their own malloc, etc.