So a little background. I'm not into Chaos Marines just yet. I'll have to wait until I get my Christmas money to start gathering my army(ies). My main force will be Khorne, which I plan on turning Apocalyptic.

I want to make a "special character" for my individual armies (1 for each Chaos legion eventually), and I'm in the idea stage right now. I haven't even bought the Codex yet, so sorry if I seem somewhat unknowledgable.. Here goes -
Khorne Lord - I've already made this guy.
Lord in Terminator Armor with a
TL Bolter, Lightning Claw, Daemonic Weapon, and Mark of Khorne. His special rule is Furious Charge, like that of the Khorne Berserkers.
The Lightning Claw is there for looks mostly, but my friends will let me use it as well as long as I pay the extra points for it. He's obviously going to be for killing things, lacking in his own survival. I will probably make a power armor version later on.
Nurgle Lord - I've decided on what this guy will be like already.
Lord in Terminator Armor with a
TL Bolter, Daemonic Weapon, and Mark of Nurgle. His special rule is Feel No Pain, like the Plague Marines. I want him to be sort of a survivalist assaulter.
Slaanesh Lord - I can't decide between giving her some kind of big doom siren or some close combat specialness. I'm leaning towards the doom siren, though. I want her to be a shooting "rain of death" type leader.
Lord with Boosted Doom Siren, power weapon, and Mark of Slaanesh. Her special rule is ???? I don't know what to give her.
Tzeentch Sorcerer - This guy should be pretty straight forward really. I want him to be a survivalist shooty kinda guy.
Sorcerer in Terminator Armor with Daemonic Weapon, Bolt Pistol, and Mark of Tzeentch. His special rule is ???? I thought of giving him a sort of "force field". Something along the lines of "If a unit fires at the Sorcerer or any unit he is joined with, your opponent must re-roll all his successful rolls to Hit." But if someone has a better idea please let me know.
So does anyone have any ideas for the last two? I'm mostly struggling with special rules. I want them to be good and give a new spin to the armies, but I don't want to make them overkill.
Any help is greatly appreciated!