Starting with #7.
First of all, severed head in a bowling bag: that gets you into the top ten off the bat. But this episode stands out not so much for the shock of Ralph Cifaretto's murder (and disposal) as for what it says about Tony. Ralph's son is badly injured in a bow-and-arrow accident; meanwhile, a stable fire kills Tony's beloved racehorse Pie-Oh-My. When Tony accuses Ralph of setting the fire for insurance money, Ralph make a denial that sounds like an admission ("It's an animal!"). They fight; it gets out of control; Ralph ends up dead. But what's most chilling is what Tony says just before killing Ralph—that Pie-Oh-My never did anything to hurt anyone—which is almost exactly what Ralph said earlier about his son. Tony doesn't just kill Ralph, he sends him out of the world equating his innocent child's life with Tony's horse's, which pretty much sums up Tony's moral universe.