What are the unused but useful feature you know in D?

[Adam D. Ruppe via Digitalmars-d]

On Sunday, 25 June 2017 at 23:21:25 UTC, aberba wrote:
> Can you share feature(s) in D people are not talking about 
> which you've found very useful?

I actually like anonymous classes. D took it from Java and D has 
a lot of other ways to do it too, but I've found anonymous 
classes to be nice with using my gui lib... and the only time I 
see other people talk about them is wanting to remove them from 
the language!