The Dunmer voices.
I have been a fan of the Dunmer since Daggerfall.I find them personally to be the most interesting race of all,with their alien,sometimes controversial culture and its many manifestations,from the honorable Redoran noble houses,to the slaving house Dres,to the wild ashlanders and their customs.
Again this might be subjective but the lynchpin of Dunmerness is their raspy voices (at least for the Vvardenfel locals).
Both the Oblivion and Skyrim demos featured a Dunmer with a raspy voice,while in the final versions,the Oblivion Dunmer spoke like the british royal family and the Skyrim Dunmer spoke like the sniper from TF2.
I really wonder.Why the deception?It's not a gamebreaking flaw but it does kill immersion for me to the point where I specifically avoid talking to any dunmer if I can help it.
Here's an of Dunmer voices for anyone who missed the earlier games.Click on the 2:00 mark to hear the Indoril guard (the guy saying "We're watching you...sssscum").
http://www.youtube.com/watch?v=jG8OjKiGAvE