Marked for Death, without a doubt. Especially useful against groups of enemies. Shout into the fray, then start swinging. Each progressive kill will be easier since their health and defense have both been depleting since you Shouted. Also, with builds that aren't as physically powerful as a heavy armor-wearing, battleaxe-wielding warrior, this Shout is invaluable against bosses. When I'm facing a Draugr Death Overlord with my archer whose arrows do but a tiny fraction of damage, I use Marked for Death and then kite him around for a minute, dodging his blows and healing myself when necessary, while the Shout does the dirty work for me... and then I start shooting.