Disable Admin Bar

Drop this code in functions.php to disable the admin bar

/* Disable the Admin Bar & Setting in Profile. */
add_filter( 'show_admin_bar', '__return_false' );
 
function jr_hide_admin_bar_settings() {
?>
	<style type="text/css">
		.show-admin-bar {
			display: none;
		}
	</style>
<?php
}
 
function jr_disable_admin_bar() {
    add_filter( 'show_admin_bar', '__return_false' );
    add_action( 'admin_print_scripts-profile.php', 'jr_hide_admin_bar_settings' );
}
add_action( 'init', 'jr_disable_admin_bar' , 9 );

Source