My final crew right now...
Killing Machine: Target their commander
Jinkster: Infiltrate and sabotage
Mama Mia: Mum Missle
The third slot I sometimes use Gooshido so he can steal more advanced ammo that I don't have, or Blubba, since I can shoot him at the enemy tank, and if he makes his way inside and survies, he'll steal 3 pieces of ammo for me to use.
I like Mama Mia since I think she does significant damage (up to 125 which is the highest I've seen from any weapon) but then sometimes she will do only 60 or something, so I think it's random. Either way, she makes good ammo.
The only way you loose an item is through alchemy or if you sell it, so feel free to throw as many rare items into your ammo as you want.
Haha, yeah, fighting the boss the second time was awesome!
As for goodybags, the backwoods were the place for me. It's the only enemy that spawns there. Still pretty rare monster tho. :S