Furnace , Hexing pands and zodiac ring are best for cube for WW barb.
hm zodiac if u play with ik weapon then its a bad choice, then better is skull grasp maybe. but yeah furnace and hexing are the most obvious choises to use.
Skull Grasp is not worth the time to cube.
I would say:
2. Hexing Pants
3. Unity or CoE
2. Hexing Pants or TnT
3. Unity or CoE or RoRG
It really depends what you want to do. I completely agree with Thornagol and I would like to add the following for solo progress:
1) Solo Bul Kathos WW Barb (cooldown build): Furnace/Pride of Cassius/Obsidian in the cube and wear Fn'R and a good String of Ears.
2) Solo Bul Kathos WW Barb: Furnace/Pride of Cassius/Unity and again wear Fn'R, String of Ears and equip your follower with a Unity of course.
EDIT: Best DPS combo for 4-member speed runs 42+ (if you do NOT want to play the cooldown build, for some reason I don't):
When you have another Barb in your party sharing his speed with Chailanic's Chain mighty belt you can use the following combo for maximum DPS:
In the cube Furnace/Hexing/CoE and wear Fn'R, Witching Hour (7% IAS, 50 CHD) and Lacuni or Steady Strikers bracers (% PHY, 6% CHC, 7%IAS). For Gems BotT/Taeguk/BotP. Use Furious Charge (Merciless Assault rune) to proc the Fn'R every 4-4,5 seconds and everything just melts.