WarplockMonkey:
Nakai of the First Spawing
Basically one of the oldest mortal creatures in existance, who is a pain in the side for daemons 
Come on…i have to keep up the scaley side! For if not me who will!
Godbob and his jolly rogers:
ah yes thank you warplock you’ve remided me about my frist army lizardmen and so it’ll have to be lord mazamudia i mean the oldest living slann riding a stedadon what’s not to love
turquois dwarf:
Lotl.
he survived the scavens plague. then he single handedly held a lizardman temple. when the relief force arived they found him surounded by hundreds of slaughtered scaven.
PhilCollinsCarnifex:
Tzarina Katarin -the Ice Queen
I own like 4 of her-she’s awesome 
the only one who can use Ice Magic lol
Ghoritch, the rat ogre character-he is hilarious
and of course Lumpin Coop
DARKTROOPER:
Konrad Curze? Hell yes! Besides him I’d say either Logan Grimnar or Boris, master of the bear cavalry!
TheVoice:
For the coolest name, Amniach the Golden (alas, confined to a short filler story in some army book or WD article).
In game and probably overall, Nagash.
Dieter Helsnicht is also up there just because he was interesting and different.
Sousunou:
malekith,be'lakor,nagash,archon,balthasar gelt,settra,malus and lord kroak are my favouriteImagine that lot in a fight! :cheers
Godbob and his jolly rogers
I will say in terms of fluff Mengil Manhide or Tularis as mengil killed, skinned and ate his brother and tularis skinned his son alive for stealing his power and then left him hanging in his basement.
In terms of model, 40k deathbringer (necron) and a tie in fantasy between Mr. Grimgor and 'Grey Seer Thanquol and Boneripper' (skaven)
For gameplay - has got to be Shadowblade. I had a battle with hashuts blessing where shadowblade caused 1 wound, which was ward saved, broke from combat and was overrun, exploded and took 1 chosen chaos warrior with him... Good times... :)
Captain Crayon:
Azhag the Slaughterer for me.
An animal of an orc semi-controlled by an ancient liche, and riding a Wyvern.
Baggronor:
Malekith the Witch King.
Closely followed by Vlad von Carstein.
Although in gameplay I’m rather enjoying Mannfred at the moment…
Lord Zarkov:
Nagash, Malekith, Mazdimundi
and good old Richter Krueger
Godbob and his jolly rogers:
ok i’ve heard who’s your faverite but who’d win in a fight beteen all that have mention (new one can be posted) i’d say grimgor maybe nagash manfredd might or the emperor on griffin you deside
TheVoice:
Nagash. If he were as powerful on the board as he is in the fluff, there wouldn’t even be a contest.