Anything that isn't symmetrical. Mice and keyboards. Circular saws. Tape measures. Box cutters. Folding knives. Garden tools. Those are just ones that impacted me recently.
Some have lefty versions but there is less selection. I recently found a left-handed weeding sickle and it is the best thing. Most of them are just annoying. I can do most things with right hand but then have to switch hands instead of the natural motion. But there are a few that are dangerous.
Measuring cups are a peeve of mine. They almost always have the handle on the right for US customary units. I had hopes of finding one biased for righty metric / lefty US in Canada but they haven't fully committed to the change yet.
More used keys like enter, backspace, arrow keys, and number pad are under the dominant hand. It isn't a big deal since most people are ambidextrous with keyboards. But there are left-handed keyboards.
The other annoyance is that default mappings for games are for left hand, right mouse. Either have to remap everything or play right-handed like I do.
I've learnt to mouse and keyboard the right handed way because it would just be too much hassle to switch over every setup I'm presented with. It does make me atrocious at drawing with a mouse though
Scissors are the other big one; most of them are designed so that when to try to use them with your left hand, you end up pushing the blades apart slightly so they don't cut as well (or at all).
With that being said, self-deprecating jokes about how left-handedness is an affront to God are definitely a prominent feature of lefty culture.
(Edit: I guess formal place-setting is another area of society that assumes right-handedness, as well as restaurants that pack people close enough together that everyone needs to use the same hands to avoid elbowing each other.)
I prefer right-handed scissors because you can see the cut line better when using them left-handed. It does take some technique to keep the blades shearing.
it's all over the place. when you hold a pen or pencil in your right hand, any text is right-side up. put it in your left hand; the text is now upside down.
there are millions of little things like that. millions. right-handed people will never ever notice them. left-handed people can not avoid noticing them.
pens & pencils
notebooks.
IP phones.
headsets (they have the mic on the left so you can scratch your face with your right hand without bumping the microphone.)
monitors (controls are on the back, right-hand side)
keyboards
mice
AND THIS IS JUST THE THINGS THAT ARE PRESENT ON MY DESK RIGHT NOW.
badge readers are always on the right-hand side of a door.
power buttons are always on the right, even on remote controls.
etc., etc., etc.
everything that is asymmetrical in any way is biased for right-handed people around 99.99% of the time. I occasionally get something from China which has accidental bias for left, but those things also have no obvious thought to the usability of anything at all.
it is maddening seeing this all day every day everywhere you go. "you are not like us" is all I get out of it and it just chips away at me with a microscopic chisel.
The industrial design and the UI design of all things tends to default to the 85% of people who are right handed and aren’t aware of potential limitations.
This is translated into issues into the items others have listed.
Some have lefty versions but there is less selection. I recently found a left-handed weeding sickle and it is the best thing. Most of them are just annoying. I can do most things with right hand but then have to switch hands instead of the natural motion. But there are a few that are dangerous.