* Hash maps in the standard library (every so often I have to go and look it up to remind myself that no, I’m not imagining things, C++03 really didn’t have hash maps in the standard library, as ludicrous as that sounds)
C++ doesn't like making arbitrary choices in standard libraries, and there are lots of performance tradeoffs and API shape choices to make in a language like C++ that refuses to make programers pay for anything they don't want.
* Hash maps in the standard library (every so often I have to go and look it up to remind myself that no, I’m not imagining things, C++03 really didn’t have hash maps in the standard library, as ludicrous as that sounds)
* Regexes
* Option and Variant types
* Move semantics
And my personal favorite...
* foo<bar<quux>> is no longer a syntax error