If you want to give other users the choice of using the admin bar, you can let them turn it off in their profile if they don’t care for it. You can choose those options in your own profile as well. If you are a single user, and want a plugin you can turn on and off, this plugin works well.
http://wordpress.org/extend/plugins/disable-admin-bar/installation/
If you want to remove it for everyone, permanently, create a directory inside /wp-content named mu-plugins, and place the above plugin file inside of it.
The readme file inside the plugin directory contains instructions.
“Disable the Admin Bar.
== Description ==
Disable the Admin Bar that now appears on the public side of WordPress blogs.
For a hassle free integration, drop the plugin file into wp-content/mu-plugins (create the directory if needed) and it will be automatically activated.”
