I voted for Alvarr because his story hasn't concluded for his last appearance. Runner-up: Odin!

Why Nimueh!? Her screen time is over! If you want her back, read this, link

I didn't vote Alverr cause there were some spoilers he will appear.
I didn't vote Nimueh cause she's dead and her revival would ruin the plot, although I'd like to see her very much.
I voted Gilli, I liked him and I'd like to see Merlin's old friends figthing with him against Morgana and Mordred with their magic.

Alvarr

And Alvarr

... And Lancelot! Why isn't he a choice?

Okay, maybe it would be just a little odd if Lance came back from the dead AGAIN. xD I just won't him to be gone forever! Not now! :( We have not seen enough of him! And that betrayal the producers had made with "their own little twist"! Argh! Why did they have to kill him off already? I mean, it's like that betrayal really wasn't that important as it seemed to be through the first 3 seasons! :/ *sigh* Well, if they make the magic reveal as the the betrayal, I'm going to sit in the corner of my room and cry the rest of my life... :C

Lancelot wasn't a villain!

Besides, they have confirmed that he won't be returning :*

i liked her better than morgana

^I can understand ;) (less smirking XD)

oh i love nimoeh..