@Vexx: Lethal Archery. I don't have many mods installed (Skyrim doesn't really need much, it's a great game even vanilla), but that was one of the things I wanted to address. I had a blast as a sniper in Fallout 3 and New Vegas, but the same playstyle is impossible to recreate in Skyrim without mods.
Re: dagger to a sword fight, I have Chillrend for that purpose, and I have favorited both my ancient DB armor (backstab mode) and my Nightingale armor (hack and slash mode). If I get detected before stabby-tiems, I switch to the other gear. Chillrend does such an absurd amount of damage on its own that with power attacks and dropping Mayhem bombs I can fairly easily wipe out entire groups with little trouble.
Usually though, one on one? I just stab them once in the ass and they die. The game occasionally glitches and registers the hit as a normal hit and not a backstab, though. But elder dragons, dwarven mechs, giants, draugr deathlords... if I can get the drop on them (abusing invis potions and the Nocturnal vanishing talent) they're dead in one hit.
My assassin character gets a 30x multiplier on dagger sneak attack (15x from talents and then double damage from ancient brotherhood gloves) and I carry the strongest dagger in the game (Blade of Woe) which has max upgrades. With 100 one-handed and all the damage-increasing 1H talents, the dagger's per-hit damage is 67. Multiply that by 30 and you get a big number.
I have not yet encountered an enemy that doesn't die in one backstab. This is with no mods, completely vanilla.