What is your favorite D feature?

[Jon Degenhardt via Digitalmars-d]

On Thursday, 22 June 2017 at 00:48:25 UTC, Seb wrote:
> Hi,
>
> I am currently trying to modernize the D code example roulette 
> on the dlang.org front page [1]. Hence, I would love to hear 
> about your favorite feature(s) in D.

A couple more:
- std.conv.to - Safe, convenient conversions that just work.
- std.regex - Really well done. May be hard to illustrate all the 
capabilities in a few examples
- Pragmatic functional programming constructs. No guessing about 
performance. Purity with local mutable variables. Interaction 
with UCFS.

--Jon