Many federal, state, and local laws exist only because of the citizenry's tendency toward inconsiderate and entitled behavior in public. While I've split this peeve list into three categories (litter, auto, and pets), it's not about those things, per se, but about the quality of routine public interactions.
Litter
I am so diametrically opposed to littering that I cannot even begin to comprehend the mindset of one who litters.
To supplement my running, I used to go for walks in the afternoon. At first, the walks were just walks, and nothing more. Then I started to notice litter everywhere I went. So I started picking up a couple bottles or cans on my way home. That wasn't cutting it, so I started to bring a single-use plastic grocery bag and fill it. Then I bought a bunch of white cotton gloves to protect my hands. Then I upgraded my plastic grocery bag to something larger and sturdier. Even with this setup, I'd find that, occasionally, I'd still fill my bag to the brim and have to walk past more litter. So I started wearing a backpack, which could comfortably hold a single full litter bag and keep my hands free for other litter bags. I learned about the location of all the public trash cans so that I could offload at least some of my trash while I was out. I then discovered a public recycle bin at a local elementary school, and this has been a game-changer: I can now offload all of my trash while out, and continue picking up trash without stopping at home. This is my current setup, but I'm open to evolving it if I see a need, or an opportunity.
Most of my haul tends toward food trash: bottles, cans, plastic cups, paperboard, wrappers, etc. The majority of the rest tends toward what I would call "road debris" and could include pretty much anything. If you can imagine it, I've seen it — aside from human remains. I haven't encountered that yet.
There are levels to littering: If you've thrown an apple core into a thicket or wooded area, I can acknowledge your rationalization. (And I don't bother with such quickly biodegradable material.) The next level would be empty bottles and cans. An eyesore, but routine and easy to pick up. Next up are vessels still containing liquids/solids. I've put that delicately. Worse still is premeditated dumping: bags full of random detritus, half-eaten fast food meals, and used diapers. The absolute worst are dog walkers who take the time to carefully bag their dog's excrement, but leave the bags right there by the sidewalk for someone else to deal with. This is actually a thing and it's prevalent.
What really gets my goat, though, are people who litter in otherwise pristine and scenic areas. Let me set the scene: you're a person who enjoys the great outdoors: fishing by a lake or river, mountain biking or hiking on a forested natural-surface trail. Like many people, you're drawn to the peace and untouched beauty of nature. However, you are also very thirsty and your predisposition to littering in situ trumps your desire to — at the very least — preserve the pristine, natural environment that you're ostensibly enjoying. Huh? Imagine the preposterous Venn diagram of people who meet this criteria. And yet, I've routinely spent afternoons pulling bag after bag of trash from the banks of beautiful lakes and from trailheads.
The elephant in the room here is alcohol-related litter. The presence of alcoholic beverage litter implies the public consumption thereof. Again, whether or not laws restricting the public consumption of alcohol are reasonable is out of scope for this blog post. Personally, I am ambivalent on the matter. But I'd estimate that close to half of beverage litter (bottles, cans, etc) is alcoholic. This is true even of road debris: trash likely tossed out of vehicles and not by pedestrians. Perhaps those who routinely drink and drive are more likely to litter — in order to get rid of the evidence?
Lawn signs in the public right-of-way
This is a relatively recent pet peeve for me. My only explanation is that people are just unaware that you can't use the public right of way (the clear zone) to erect lawn signs to advertise your business. The worst offenders are freelance manual laborers: roofers, junk removers, plumbers, electricians, mechanics, and landscapers. Most signs from real estate agents and home builders are also unlawful. While unwieldy and difficult to dispose of, I've started to pull lawn signs.
Auto
Abuse of handicapped placards/plates
I have no direct evidence of specific instances of abuse. Further, I realize that some disabilities are not outwardly apparent. However, almost without fail, when I observe people using designated, accessible parking spaces, they appear to be just as able-bodied as you or me. No wheelchair, walker, crutches, awkward gait, etc. Perhaps I betray my ignorance on the matter, but when I see a car parking in an accessible spot, I expect at least one of the occupants to be genuinely physically disabled and to materially benefit from the convenient proximity of the designated parking space.
Idling for extended periods
As the owner of an EV, I am much more attuned to idling violations. I notice idling everywhere now: in shopping center parking lots, near parks and playgrounds, on streets as I walk by. Aside from the pollution and deleterious health effects, exhaust just straight up smells horrible. Idling near people and pedestrians is an anti-social activity, full stop. (No pun intended.)
Many are still under the assumption that one must idle their car in cold weather, prior to driving. Not so; when you're ready, you can just start moving. Your engine may not be optimally efficient for a few minutes as it warms up, but then again, while you're idling, you're guaranteed to get zero MPG. How's that for efficiency?
Ignoring stop signs
Whether or not a stop sign at any given intersection is the best way to calm traffic is beyond the scope of this discussion. But if there's a stop sign, assume that everyone else — especially pedestrians — are going to behave as if other people will be obeying said stop sign. I've seen people take "rolling stops" to a whole new level: instead of speeding, they'll temporarily go the speed limit — through a stop sign.
Exceeding sound limits
As the owner of an EV (see a trend?), I am much more attuned to sound violations — I can't prove it, but my environment seems to have gotten louder since acquiring an EV in 2019.
80 decibels max is Maryland law. The typical motorcycle (with stock exhaust) lands at about 80 decibels while idling. Modified bikes can easily be four times as loud. Whenever I hear one, I think, that's gotta be illegal, and I was right. Electric motorcycles can't come fast enough.
I pick on motorcycles, but modified cars can be just as loud. Some drivers seem like they're getting paid for each exhaust growl, pop, or bang that their cars emit. On many occasions, it sounds as if my neighborhood is taking incoming mortar fire from the IDF.
Speeding (corollary: going far below the speed limit)
Read the room, as it were. Your main job as a driver is to keep from getting noticed — either by risky maneuvers or by traveling outside of the generally-accepted speed range. What is this range? My hunch says the posted speed limit plus/minus 10. Again, whether or not a particular road's speed limit is reasonable is out of scope here. But if you're exceeding the speed limit to the point of tailgating or driving slow enough to predispose others to tailgate you (reverse tailgating), then you need to be corrected.
Parking in close proximity to mailboxes — especially mine
Yes, blocking a mailbox is actually a violation of 18 U.S. Code § 1701. Not to mention, it's monumentally annoying when neighbors — mostly, people I've never met — do this.
Pets
Unleashed dogs (or "At large", to use county parlance)
Generally, if you encounter an unleashed dog, the owner is breaking the law. At least where I'm from. While some people welcome attention and contact from random pets, I personally don't. Random dogs are less predictable than little children (and are much more likely to bite if startled.) This comes to the fore when I'm trail running and encounter dog owners who intentionally unleash their pets in the woods. I don't want a collision and I certainly don't want holes in my calf muscles.
Honorable mentions: not unlawful, but frowned upon
Parking
Aside from the mailbox issue, I will concede that the street in front of my house can be used for public parking and is first-come first-served. However, I still consider it to be my own residence's temporary "visitor's parking." But it's rarely used by legitimate visitors. Rather, neighbors — mostly, people I've never met — use it for their own long-term overflow parking. Sometimes days or even weeks at a time.
Loud/unruly dogs
Opting out
Having to continually unsubscribe from all manner of marketing calls, texts, emails, and paper mail from seemingly every company or organization that I interact with. Never in my life have I ever explicitly signed up for any of it!
Loud phone calls, especially on speaker
Imagine the quick buzz of a mosquito in your ear. Now, amplify that one-hundred fold. That's what your speakerphone sounds like to me. It's a violation of the social order to the highest extent.
The following link dump represents the web developer tools that I use most frequently, both 
The propensity of a person to play back recorded sound in public and unsolicited (for instance, in a store, at the park, or while in the presence of a captive audience such as on the subway) is inversely proportional to the generally-accepted listenability of the music being played and the quality of both the source and the playback equipment.
