A plugin to modify the TinyMCE editor in WordPress 3.9+. Now available on WP.org! https://wordpress.org/plugins/mrw-web-design-simple-tinymce/

readme.md

Now available in the WordPress.org Plugin Repository: https://wordpress.org/plugins/mrw-web-design-simple-tinymce/

mrw-tinymce-filter-example.php

<?php
/**
 * Example filter to add text style to TinyMCE filter with Mark's "MRW TinyMCE Mods" plugin
 * 
 * Adds a "Text Styles" submenu to the "Formats" dropdown
 * 
 * This would go in a functions.php file or mu-plugin so you don't have to modify the original plugin.
 * 
 * $styles 	array 	Contains arrays of style_format arguments to define styles.
 * 					Note: Should be an "array of arrays"
 * 
 * see tinymce.com/wiki.php/Configuration:style_formats
 * see also tinymce.com/wiki.php/Configuration:formats
 * see also also wordpress.stackexchange.com/a/128950/9844
 */
add_filter( 'mrw_mce_text_style', 'mrw_add_text_styles_example' );
function mrw_add_text_styles_example( $styles ) {
	$new_styles = array(
		/* Inline style that only applies to links */
		array(
			'title' => "Link Button", /* Label in "Formats" menu */
			'selector' => 'a', /* this style can ONLY be applied to existing <a> elements in the selection! */
			'classes' => 'button' /* class to add, could be multiple, space-separated */
		),
		/* Inline style applied with a <span> */
		array(
			'title' => "Callout Text",
			'inline' => 'span',
			'classes' => 'callout'
		),
		/* Block style applied to paragraph. Each paragraph in selection gets the classes. */
		array(
			'title' => "Warning Message",
			'block' => 'p',
			'classes' => 'message warning'
		),
		/* Block style capable of containing other block-level elemeents */
		array(
			'title' => "Feature Box",
			'block' => 'section', 
			'classes' => 'feature-box',
			'wrapper' => true
		)
	);
	return array_merge( $styles, $new_styles );
}

mrw-tinymce-mods.php

Now available in the WordPress.org Plugin Repository: https://wordpress.org/plugins/mrw-web-design-simple-tinymce/

@cbournak Check out @ryanderson's (I think that's whose it is) question on WPSE. I believe the table buttons suffer from the same issue in that WordPress doesn't include that TinyMCE plugin by default. You'll probably need a plugin like MCE Table Buttons to get it working. (And for the record, I much prefer using TablePress as it discourages users from getting all layout-happy with their tables.)

@bryanwillis You're right that that's a limitation of this plugin which I mostly made for personal use. I prefer the styleselect for it's custom text styles functions that aren't available in the Formatselect.

For anyone who missed it above, this is now a plugin: https://wordpress.org/plugins/mrw-web-design-simple-tinymce/