Depends on the type of PK'ing I am doing.
If I am out to anti-PJ I usually just wear Torags Plate+Legs, Niet Helm, Skill Cape, Strength Ammy, Zerker Ring, Obby Shield and Whip. I have Korasi or D Claws in inventory for spec.
As far as Runes, if I am anti-PJ'ing I bring Disruption Shield and Vengeance.
Food I bring Rocktails, 2 Brews, 2 Pies, 2 Prayer Potions.
Works pretty well. Rushers get dumbfounded when their first hit does nothing because of Disruption Shield.