HTML5 has made it a lot easier to include certain elements. Especially videos, since you no longer have to embed them with all those parameters. Here’s a short code snippet that will add an HTML5 video shortcode to WordPress. Just include this code in your functions.php file and you are ready to go:

function html5_video($atts, $content = null) {
		"src" => '',
		"width" => '',
		"height" => ''
	), $atts));
	return '<video src="'.$src.'" width="'.$width.'" height="'.$height.'" controls autobuffer>';
add_shortcode('video5', 'html5_video');

Now you can use the following shortcode in your post:

[video5 src="http://your-site/videos/your-video.mp4" width="720" height="480"]

You can read more on which browsers support which formats at