A terrible gift

[Brendan]

If I gave a present to a human fighter: a viscous human bane greataxe, would an extra 2d6 damage happen to the fighter every hit, as well as the d8?

[shadow_archmagi]

If I recall vicious correctly, no.

The sword isn't actually hitting the fighter; he's just suffering magical whiplash.

[RS14]

Vicious normally deals 1d6 to the wielder, not 1d8.

I would rule that it does not deal extra damage to a human wielder, because it is not being used against the wielder.

A bane weapon excels at attacking one type or subtype of creature. Against its designated foe, its effective enhancement bonus is +2 better than its normal enhancement bonus. It deals an extra 2d6 points of damage against the foe.

[Altair_the_Vexed]

If I recall vicious correctly, no.

The sword isn't actually hitting the fighter; he's just suffering magical whiplash.

Yup - the Bane damage won't stack with the vicious:

Vicious: When a vicious weapon strikes an opponent, it creates a flash of disruptive energy that resonates between the opponent and the wielder. This energy deals an extra 2d6 points of damage to the opponent and 1d6 points of damage to the wielder. Only melee weapons can be vicious.

Gah! Ninjas everywhere...

[Thurbane]

Then there's the other FAQs about the damage Vicious does to the wielder:

Is it reduced by DR?

Can it be blocked with Resist Energy/Deathward?

If it is negative energy does it heal undead?

If you combine Vicious with Merciful, does the damage become non-lethal?

[Starbuck_II]

Then there's the other FAQs about the damage Vicious does to the wielder:

Is it reduced by DR?

Can it be blocked with Resist Energy/Deathward?

If it is negative energy does it heal undead?

If you combine Vicious with Merciful, does the damage become non-lethal?

It is untyped magic damage.

So in order:
1) no.
2) No.
3) No.
4) Maybe.