I read a great description of my favorite aspect of Ruby in The RSpec Book, by David Chelimsky, et al. It was so apt, I had to share it. Here it is (emphasis mine):
When first learning Ruby, you might get a sense that the language is
reading your mind. Say you need a method to iterate through the keys
of a Ruby hash so you type hash.each_pair {|k,v| puts k} just to see if it
works, and, of course, it does! And this makes you happy!
Ruby is filled with examples of great, intuitive APIs like this, and it
seems that developers who write their own code in Ruby strive for the
same level of obvious, inspired by the beauty of the language. We all
want to provide that same feeling of happiness to developers that they
get just from using the Ruby language directly.
Well put.