The military has a lot of rules and some of them are hard to follow every day in every instance. We're not saying that everyone should be prosecuted under any of these articles, we're just saying that a lot of people technically break these rules.
1. DISRESPECT TOWARD SUPERIOR COMMISSIONED OFFICER (ART. 89)
"Any person subject to this chapter who behaves with disrespect toward his superior commissioned officer shall be punished as a court-martial may direct."
"Can't spell lost without the LT!" called in cadence in the presence of an officer is technically a violation of Article 89.
Interestingly, this is one of the few times where the word, "toward," in an article doesn't require that the victim be present. Service members can be prosecuted under Article 89 for disrespecting an officer even if that officer didn't hear or see anything. For the NCO equivalent listed below, the NCO or warrant officer must be present and hear or witness the disrespect.
2. INSUBORDINATE CONDUCT TOWARD WARRANT OFFICER, NONCOMMISSIONED OFFICER, OR PETTY OFFICER (ART. 91)
"Any warrant officer or enlisted member who–
(1) strikes or assaults a warrant officer, noncommissioned officer, or petty officer, while that officer is in the execution of his office;
(2) willfully disobeys the lawful order of a warrant officer, noncommissioned officer, or petty officer; or
(3) treats with contempt or is disrespectful in language or deportment toward a warrant officer, noncommissioned officer, or petty officer while that officer is in the execution of his office;
shall be punished as a court-martial may direct."
Anyone who has mouthed off to a superior NCO or warrant officer is guilty, provided they knew that the person was an NCO or warrant officer at the time. Talking back to a squad leader could trigger Article 91. This also covers assaulting or disobeying a lawful order from a superior NCO or warrant officer.
3. MILITARY PROPERTY OF UNITED STATES-LOSS, DAMAGE, DESTRUCTION, OR WRONGFUL DISPOSITION (ART. 108)
"Any person subject to this chapter who, without proper authority–
(1) sells or otherwise disposes of;
(2) willfully or through neglect damages, destroys, or loses; or
(3) willfully or through neglect suffers to be lost, damaged, sold, or wrongfully disposed of;
any military property of the United States, shall be punished as a court-martial may direct."
Getting the corpsman or medic to give an unnecessary I.V. or walking off with a couple of MREs falls under Article 108. Even painting hilarious graffiti on a bunker counts.
Side note: Some people like to claim that this article forbids troops from getting sunburn because that's damage to "government property." The Stars and Stripes Rumor Doctor investigated this and experts in military law told him this isn't true for two reasons. First, service members are not military property. Second, the government has to quantify the damage done to the property which is nearly impossible when referring to a human being.
4. PROPERTY OTHER THAN MILITARY PROPERTY OF UNITED STATES - WASTE, SPOILAGE, OR DESTRUCTION (ART. 109)
"Any person subject to this chapter who willfully or recklessly wastes, spoils, or otherwise willfully and wrongfully destroys or damages any property other than military property of the United States shall be punished as a court-martial may direct."
This article is pretty broad, referring to any willful or reckless destruction of someone else's personal property. So service members who vandalize a porta-potty rented from a vendor are technically guilty. In practice of course, the damage needs to be worth investigating and the government has to prove a certain person committed the act at a specified place and time.
5. GENERAL ARTICLE (ART. 134)
"Though not specifically mentioned in this chapter, all disorders and neglects to the prejudice of good order and discipline in the armed forces, all conduct of a nature to bring discredit upon the armed forces, and crimes and offenses not capital, of which persons subject to this chapter may be guilty, shall be taken cognizance of by a general, special or summary court-martial, according to the nature and degree of the offense, and shall be punished at the discretion of that court."
There are many ways to fall foul of Article 134, but the most common is probably using indecent language. Any indecent language, especially if it causes "lustful thoughts," can trigger the article.