WP Heading Buttons is a WordPress plugin by tercan that aheading buttons (H1, H2, H3, H4, H5, H6) to TinyMCE editor.
TinyMCE is a platform independent web based Javascript HTML WYSIWYG editor control released as Open Source under LGPL by Moxiecode Systems AB.
Download: http://wordpress.org/extend/plugins/wp-heading-buttons/