作るかもしれないgem

reserved_string_gem.rb

# 知見 - 登録されるとつらいユーザー名リスト - Qiita http://qiita.com/phimcall/items/4c559b70f70ea7f1953b
require 'reserved_string'

ReservedString.configure do |config|
  config.strip_string     = true # default
  config.use_default_list = true # default
  config.lists = { 
    your_list:    %w(foo bar baz), 
    another_list: %w(hoge piyo),
  }
end

"foo".reserved? #=> true
"foo".reserved_in_your_list? #=> true
"hoge".reserved? #=> true
"hoge".reserved_in_your_list? #=> false