The Kan Wall is good, not as good as it used to be back in 5th, but it is still a lot of AV11 running around.
Anyways I am surprised no one has mentioned Biker Nobz. Weapon Skill 5, 5 toughness, 2 Wounds, Hammer of Wrath, 18" S5 AP5 Assault 3 Twin-linked guns, 4+ Armor Save, 4+ Cover save (at all times), 5+ Invu save, Feel No Pain, and as many Power Klaws as you want. Costly? Yes, but very very hard to kill, and able to kill a lot of things.
Peace, Love, and Mass Destruction
Necrons in 6th Edition W: 28 L: 9 D: 5
Orks in 6th Edition W:9 L:9 D:3
F*** that, Barrel rolling monolith all the way.