I'm only lurking on the D forums, so this should probably be taken with a grain of salt. From what I understand the GC is required for various array, hash map and string operations, and things like closures and exceptions (maybe assertions?). Though there is work being done on fixes and alternatives (scope limitations, ref counted things).

This does seem to come up sometimes. I'm wondering if it makes sense to add a "end-vision for GC-less D" section to the D GC documentation, now that there are various undertakings to make it easier. Might also help with finding volunteers that care about @nogc to help out with various bits.