Predator. Illusion and Sneak, turn go invisible, stalk your prey, move in for the backstab and take 'em out without anyone else noticing then move on to your next victim. I'd recommend boots with a muffle enchant and the dark brotherhood gloves to double your backstab damage (30x!), as far as the dagger goes, you can basically use anything you want. Keep invisibility in your left hand for a quick cast for when it runs out or when you break it to stab and keep your dagger in your right.
Silent and deadly, the ultimate predator!