What's the best available open source editor/IDE for Ruby?

Possible Duplicate:
What Ruby IDE do you prefer?

I am purposing to use it for web development using Ruby on Rails. Any suggestions?

And this is a CW ;)

From stackoverflow

• NetBeans is the best. You can download the "ruby" version - so you have rails support out of the box. It has all the important features for me: debugging support, syntax highlighting, auto-formating, rake task runner, ./script/generate runner. In last three versions I used it - startup and running speed increased and number of critical bugs decreased.

  I have tried Aptana, Radrails, vim with ruby scripts, jEdit with ruby support etc .. and I have settled for NetBeans. It's very easy to "pick up" for new developers ...