Off-hand unarmed.

[roguelikedev]

I'm a big fan of the new "perks" to natural attacks conferred by mutations, although none of them seem particularly effective-- balance aside, they're cool and fun. Given that shields are very powerful and unarmed strikes with the off hand are quite the opposite, I'd like to see something similar added to them: the "constrict" ability which anacondas have. Thematically, the character is using the free hand to grapple with the enemy: choking them, gouging eyes or simply squeezing until popcorn noises are produced.

[dolphin]

I think unarmed effects are slated to go in when weapons get abilities.