Charge or Bucking Bronco. Charge really only works as a last-ditch move while weapons are reloading, or as a free health revenue with the Bloodlust (health on melee hit) gear.
I'll go with Bucking Bronco, because it just works. Toss them in the air, quickly headshot them with Bird's Eye or Handcannon, bring them all down with the Heater or RPG, or spin them around and destroy them with the Repeater, and do it again because it costs pittance salts, because it just works.
And Murder of Crows won? I thought it was a pretty sucky vigor. It effected a huge area and it stunned them, but I never got an actual kill out of it, and it hardly works against bigger enemies like Firemen and Motorized Patriots. And even still - it's never as though killing the cannon fodder enemies provided any challenge. Bucking Bronce at least uses less salts for the same area of effect, and it stuns them longer.