i'm just wondering, coz of the jarhead movie....

Only if they can, and are disposed to, kicking your ass.

Haven't seen the movie, won't see the movie , so don't know exactly what you're talking about (I was warned not to see it, it's completely retarded and not representative of the Marine Corps...or so I'm told). BUT, no as a general rule, only officers are called "sir". Some people and units develop a respect for people and call them "sir"
(I used to call anyone "sir" if they helped me out), but that's not common practice.

Being a retired GySgt, serving in a govt contractor capacity, whenever I encounter enlisted, especially junior enlisted, I address each of them with a SIR.

You would be surprised at the reactions I get. I have yet to have any of them correct me with the standard retort..." I'm not an Officer, I didn't have to be taught how to eat with a fork!" Or "I'm not a Zero, I work for living"

Top_Gun - in the Navy you will not get a response from E-6 and below however if you call a older CPO Sir he will chew your butt out that is the biggest insult you can give a CPO.E-7 and above.Kinda like you do not ever wash a CPO Mess coffee pot.

yeah, Chief Petty Officers can be pretty 'anal' about that.

Well, they do generally have the best coffee.

Ah yes. I remember meeting my first USN Chief. See, in the USMC only officers wear shiny stuff on their collars. If it's shiny, salute it. Didn't know that CPOs also wear shiny stuff on the collar....I saluted it. That was a memorable ass chewing.

only if they are a higher rank than u otherwise they sould becalling u sir

So as a Gunny, I'm required to address a Msgt as Sir?

First time I got called' Sir ' when I was a barely shaving, newly minted 2Lt, I had to turn around to see if there was a General behind me LOL..

I still chuckle when at formal/military occasions the son and daughter stumble over " Mum/Ma'am " when speaking to the Good Padre

don't know if its still ' informal' protocol but I was ' taught' you saluted and called ALL officers ' sir [ ma'am ]', all NCO's by their Rank [ Sgt.! Master Chief! , etc. ] and all other ranks [ lower than yours] as "Hey, Maggot!"

he calls his sargeant sir only until he finds out he is a staff sargeant then he calls him that for the rest of the movie