I have had a bunch of fun creating a dark character. He is a werewolf with the Ring of Hircine, and although it is difficult, the ability to throw enemies makes it playable even on master difficulty. If you flee, wait-heal, and transform again with the Ring, you can massacre whole towns on master difficulty. Possibly the darkest quest in Skyrim involves both a daedra and a macabre cult, and the reward
Spoiler The Ring of Namira and the ability to eat corpses after the Daedric quest
allows you to role play a dark player very well. I
Spoiler eat corpses as a werewolf and a as a devout worshiper of Namira, and also am a talented necromancer. This is a fun way to play a dark character and allows plenty of room for doing twisted things. Often times my character cannot control his blood lust and massacres entire villages as a werewolf, indulging on the human flesh he craves