code for removing user

app/models/user.rb

@@ -152,6 +152,13 @@ def admin?
     self.f_id == ENV['FACEBOOK_ADMIN_ID'].to_i
   end
 
+  def remove_from_application
+    LevelUserLink.where(:user_id => self.id).each { |lul| lul.update_attributes(:user_id => nil) }
+    PackUserLink.where(:user_id => self.id).destroy_all
+    UserUserLink.where(:user_id => self.id).destroy_all
+    self.destroy
+  end
+
   # Ask facebook if this user likes the facebook fan page of the application
   # return true or false
   def request_like_fan_page?

lib/tasks/app.rake

@@ -49,5 +49,13 @@ namespace :app  do
   task :flush_cache => :environment do
     Rails.cache.clear
   end
+
+  task :delete_user => :environment do
+    user = User.where(:email => 'email').first
+    # or
+    user = User.where(:name => 'name').first
+
+    user.remove_from_application
+  end
 end