I used to be a big fan of Walmart paint, mostly because of its cost. Although I find the metallics and red to be pretty good, walmart or not. For bombing, cheap paint does the job.
But when you start piecing more often you realize shitty paint sometimes just doesn't cut it. Some here would say if you got talent you can use any kind of paint and be able to work with it. I find that hard to believe in many cases. For blacks, my personal favorite is Rusto Gloss- Krylon UFB being a close second.
Oh yeah, OSHA green is sick. I wish I still had a can or two. =/