Depends on the viewer...
I love this show! Great characters, great writing, and creepy. This is the perfect show for anyone who is a horror fan. Now to the content...I personally think the iffy for 16 rating is a little extreme. Some episodes are may be okay for kids 13 and up. But as the series goes on, the more gory it gets. I have been very surprised at some of the more disturbing episodes later on in the show ("Family Remains" is one to watch out for). I've seen up to season 8, but there have been a couple torture scenes so far (nothing is really shown in great detail, but is still very dark and disturbing). To name a few of the gorier stuff that occurs in most episodes: people get teeth pulled, nails ripped out, a guy starts peeling his face away, lots of beheading, necks and wrists getting slit, any episode involving witchcraft is gruesome, disturbing shots of dismembered or eaten corpses, a surplus of blood and plenty more. Expect to see some things you'd normally see in a R rated horror film. And the beginning of every episode usually features something scary or gory. Not to mention the language gradually gets more noticeable as well: b***h (which is used all the time in every episode), ass, d**k, some uses of s**t and f**k but they are either implied or bleeped. Dean occasionally uses the word, mofo (which stands for motherf***er). As for sexual content, nothing too bad. Sometimes the dialog can be explicit. It's mostly Dean's references. Occasionally the characters go to a strip club on a case. There is usually one or two sex scenes every season, but they are not overly explicit. Last but not least, drinking. The characters drink in most episodes. Dean and Sam occasionally get drunk. Bobby is always drinking and referred to as a drunk by characters. Overall, I'm giving this a 15 and up. The first two seasons are probably okay for 14, 13, and maybe 12. Season 4 is particularly violent and seasons 4-5 will most likely offend people who are very religious. Overall, the main concern is the violence (I know some adults who can't even handle it). It depends on the episode as well. Some of the story lines can be disturbing enough without the added gore. Know your kid and watch out for most of the episodes in later seasons. Hope I've helped. :)
What other families should know
Great role models
Too much violence
Too much sex
Too much swearing
Too much drinking/drugs/smoking