Off the top of my head, mine would have to be when someone takes the garbage bag out out the trash can and DOES NOT put a fresh bag back in. Oh my dear lord this instantly gets me fired up. I have no idea why but it has just always bugged me.
Share any and all of yours. :)
Another one would have to be when driving and other drivers fail to use their blinker when making a turn. Like dude seriously it's not even two inches away from your left hand. It does not require much work at all lol.
Or when someone comes into your house and feels the need to leave their shoes on. It's common courtesy to take your shoes off unless you're told you can leave them on.
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When people call an object something that it is not. Ie. Calling a pen a marker