Shivs were doing 270 damage and Grenades about 190. So, just from using my 10 Grenades and 10 Shivs, I had Halloran down 25% from his starting health. This was going to be too easy!
But this was far from a blowout fight. My Stun Guns were not as helpful as before. They only gave me one free shot at Halloran, instead of two, and each attack of mine only did slighly more than 400 damage.
Still, after using the 10 Stun Guns, and recharging a *number* of times, the end was near:
And at last, Governor Halloran has been recalled from office.
Some commentors have correctly noted that there is no reason to use your Stun Guns, Shivs, or Grenades since you can simply go to Moscow or Cuba and recharge your health with the otherwise-useless currency there. That begs the question of what exactly one WOULD use the Stun Guns and other Boss consumables for...
Either way, once you're done with Governor Halloran at Ruby level, and assuming you've gone through the Las Vegas Distrcits in order, you're all out of Bosses. For now...