Any ideas would be good. Stealth builds are for the most part unwanted. Any evil items (things like the Tome of Unlife) would also be good.

There is this item called Volendrung.
It is a warhammer with a daedric appearance and a red glow, very evil looking.
Oh, and bump into kids.
That is very evil to, it is also very evil to NOT play tag with them.

Daedric or Ebony Armour I should think. Get some cruel looking weapon and smash people's faces in with it.

it's probably the evilest thing I've found, and it looks cool.

Heavy aromor, unarmed and explosions. Just blow stuff up and smash things in the face.

Take your fav. build and just make em evil. Kill when you want to not when you have to, take what ever you want without asking questions. Join the DB and or TG, join the companions if you want to have an animal side to match your evil side. Choose eveil/menacing looking clothing/armor like daedric armor, Ulfric's robes( my fav.) DB armor, TG armor etc...etc...
And finally evil looking weapons, ie.... daedric,ebony,orcish,ancient nord.

My evil toon wears Ulfric's robes with daedric boots and gauntlets with the nightingale hood, he uses daedric quest items and weapons,ebony weapons and kills as often as possible here's a look at em http://i1264.photobucket.com/albums/jj500/Justin_Peddle/100_6340.jpg he's the self appointed " Grim reaper " of Skyrim the weapon on his back is the headsmans axe now renamed Death's axe
He is your typical sword & board warrior with a little dual wield and some two handed.

Most of the Daedric quests seem to be quite evil. Some have evil vs non-evil paths, and you can choose the evil path.

I'm doing that with my current character who is evil. Daedric quests, Dark Brotherhood and Thieves Guild. Generally I prefer to play good characters, but I like to do a play though with at least one evil character to explore that part of the game. Some of the Daedric quests in particular appear to be some of the better quests in the game. I've only started the Dark Brotherhood so I can't comment much on that yet.

It's nice to look at but it's extremely weak as two handed weapons go.

Funny thing is, I never thought that the thieves guild were particulary evil. They just liked to make some coin.

Neither do i find the Dark Brotherhood evil.
It is just bussines, no?

Namira. That is all I shall say. Once you taste it, you will agree.

Trap ALL the souls! Get the Black Star for this.