What is your biggest pet peeve?

"goodness sake show some discipline!"
First of all having your hands in your pockets in in no way showing that you do not have discipline.
Like others have said a rule should have a good reason behind it.
I had plenty of experiences in the Navy where gloves were not an option because of the nature of the work yet there were times that it was below zero outside and the little bit of warmth made life a little more bearable.

Secondly it is the SNCO that has a warm office, a warm cup of coffee and much better accommodations that is yelling at the junior who is working out in the cold or under much more uncomfortable conditions.
Sorry but complaining about unimportant things like having your hands in your pockets while you are taking a short break and trying to base someone's career on that is just you nitpicking. And it is a reason that I am glad that I am out.

In my days as a First Sergeant I would always encounter individuals with hands in their pockets and remind them about being professional. Should they respond back with anything other than thank you or an apology I would ask them if they still had the gloves that were issued to them in basic and also if they spent their annual clothing allowance appropriately.

One of my biggest pet peeves is hands in the pockets. But equally disturbing is those that talk with their hands

Seeing service members walking around with Hickey's all over their neck like they just left the "Red Room".

When Soldiers cut the liner out of their PC so they can "Ranger Role" it or style it to their liking OR a dirty PC in general.

Rolling and Cuffing the ACU top Sleeves

Not putting Edge Dressing on your Dress Shoes

Walking in Uniform with your Phone on Speaker

Overall, I hate when I see SM ESPECIALLY leaders i.e. NCOs & Officers walk past uniform deficiencies and not say anything. I am THAT NCO that will stop you and correct you (with Tact) if you are wrong no matter were we are! I hate seeing people avoid correcting someone just because it's not their Soldier, or because he's on the other side of the PX, etc. You cant expect, what you don't inspect. Chances are, if you wont make the correction outside your unit footprint, you're probably not doing it at all, or avoid such standards yourself.

Mine was thread coming off the uniform at any point of it

Biggest irk, ink stains, black and blue ink stains. Can't stand it.

That soldier also needs to address the strings hanging off the uniform. Quick. Get the lighter!

biggest pet peeve: wearing gloves w/ out a jacket. If it's cold enough for gloves then it's cold enough to wear a jacket. And when temps are in the single digits or teens how stupid you look w/out a jacket on (I'm talking about folks w/ short sleeve uniforms in Winter and no jacket). You were issued a jacket. Wear it.

Cargo pockets on ACU trousers open. Sadly this not the Soldiers(meaning me too) fault most times. Majority of the ACUs have Velcro fasteners and after the first tug the Velcro is shot forever. I heard they are starting to issue them with buttons... if only my unit had the money so I could DX my entire issue for them.