While developing software, developers always tend to curse about some language specifics, "improvements" that made language less understandable, buggy.
What obstacles / improvements have you met, that you'd be pleased no one ever invented / introduced?
My 2 cents:
I cursed for 3 days at delphi 2009. I had an internal compiler error, with no clue what I was doing wrong. It turned out I couldn't inherit a Generic class declared in another unit.
edit: moved to community wiki, as some of comments suggested