Good plugins for rails

I want to know more plugins or gems which can help to make my rails application more powerful and efficient and easy to handle.

Like 
    mysqlplus instead of mysql
    memcached
    delayed_job
    resque
    capistrano
开发者_StackOverflow社区

I would add the following plugins/gems to your list:

1. Authlogic (or Devise)
2. declarative_authorization (or CanCan)
3. Cucumber and Capybara
4. RSpec or Shoulda
5. Factory Girl
6. Haml and Sass (with Compass)
7. Paperclip
8. will_paginate
9. Formtastic
10. Searchlogic
11. RVM (last but by no means least)

What do you mean by 'powerful'? :) Efficient - that depends on what exactly your application is doing.

Anyway, for a good eye-pick on what are your options, you may visit Ruby Toolbox.