The things that I still don't like about Ruby's syntax & semantics (even though it's my second favorite language):

  - No keyword arguments
  - No good syntax for creating pure functions
  - Metaprogramming seems tacked on
  - HERE doc manipulation is atrocious
  - There is no 'fundamental unit' of a Hash
    (other than a destructured key-value pair),
    so mapping a function onto hash keys or values
    is always a call to #reduce or a Hash[array]
  - Creating a Hash with #reduce is not pretty
  - Destructuring isn't so sophisticated
  - Local variables become defined even if they aren't in your
    current code path
  - I already mentioned method passing

These are all things, by the way, that Clojure does much, much better.