Big Bad Voodoo is a Voodoo Witch Doctor skill unlocked at level 25. This skill summons a fetish to perform a ritual dance which buffs all nearby allies with increased attack and movement speed.
This skill summons a piggybacking Fetish Shaman. That creature remains stationary once summoned, and for the duration of the skill it creates a glowing circle on the ground. The Witch Doctor and all of his allies who stand within that circle gain a buff for the duration of the spell.
Given the the lengthy cooldown and powerful benefit, this skill is best saved for battles with Elites and other dangerous enemies.
The following is a very quick summary. See the Big Bad Voodoo rune effects page for a more thorough description of rune effects, or any of the individual rune pages for numbers, screenshots, blue quotes, and much more.
The skill was first demonstrated at the July 2011 Press Event in the b-roll video. The skill appears to be 3 fetish stacked upon one another with the topmost fetish wearing a mask and waving a staff. The skill creates a green aura on the ground around the fetish which buffs party members within radius.
The beta started in September 2011, and Big Bad Voodoo became a level 24 skill. The skill system was once again overhauled for the Beta Patch 13 in February 2012, and Big Bad Voodoo was classified as a Voodoo skill and moved back to level 25.
Big Bad Voodoo has, throughout development, been too high-level to play, so there are no gameplay reports describing it.