Coming to Ruby from JavaScript (among other paths) I personally dislike
Ruby's two-character Hash delimiter. It's been brought up before, and I
know that the colon makes it harder to parse with symbols, but I wish
we had a one-char (preferably without shift on an English keyboard
layout) hash delimiter.

hash = [ foo:bar, whee~la, dunno|what, delimiter=wouldbe ]

Heck, even two no-shift chars would be a nice improvement:

hash = [ foo--bar, jim..jam ]

...but now I'm hijacking the thread.