This takes forever but I like this active-farming method. I'm level 69 (playthrough 1) and using a strong combat rifle for this, no mods.
AR490.0 Glorious Massacre
(Damage-327, Accuray 93.9, Fire Rate 8.8)
with fire element x4
+100 Magazine Size (124 shots before reload)
+76% Recoil Reduction
The only thing I've noticed so far if I kill them all very fast, there are too many items at one spot and when MINAC drives over them or the bombs he left explode near the collectibles a few simply dissapear. Looks like a glitch to me. So either I have to pick 'em up fast or get the things that are left. I want to avoid getting overrun.
So far I'm looking at:
Oil Can and 4
Bobbleheads. Oh well...
Edit: My end-stats after 5h of farming with this method:
Pizza - 18
Panties - 35
Clapfish - 37
3D Glasses - 35
Oil Can - 25
Bobblehead - 16
I died a looot but then again I also had enough money hehe. One more DLC (the best) to go and I'm done with this game.