I will rate the quirks on a scale from 1-10 (10 being the best) based on my favorites and how unique it is.

𝐏𝐨𝐰𝐞𝐫𝐬 𝐅𝐫𝐨𝐦 𝐎𝐭𝐡𝐞𝐫 𝐀𝐧𝐢𝐦𝐞𝐬 𝐓𝐡𝐚𝐭 𝐖𝐨𝐮𝐥𝐝 𝐁𝐞 𝐂𝐨𝐨𝐥 𝐐𝐮𝐢𝐫𝐤𝐬 𝐢𝐧 𝐁𝐍𝐇𝐀:

Shin from Dorohedoro - (10/10)

Power:

Shin can slice people into pieces without killing them.  For example, he could cut a victim in half, but the victim will not die of blood loss or organ failure or anything.  If not put back together, however, the victim's body is still prone to rotting.  This would be useful for interrogations and torturing.  There is no limit to how sliced up the victim can be.

Personal Thoughts:

This would be a very powerful quirk, so if this were to be used, I would say that a possible weakness would be that it takes a lot of control to separate the body parts, so after a long time, the user would lose energy to continue keeping the body parts split up.  That means that the user could either piece the body parts back together or the user could leave the body parts separated and kill the victim.

Mirai Kuriyama from Beyond the Boundary - (8.1/10)

Power:

She can use her blood to create a sword.  This is the only thing she can create, though.

Personal Thoughts:

Her weakness in the anime was that she would suffer effects of blood loss after using her power for too long.  This is a reasonable weakness.  It would be interesting if the user could learn to be a dual wielder or something.

Shigeo Kageyama from Mob Psycho 100

Power:

Mob actually has a lot of powers because he is an esper, but splitting up his various abilities, he has:

1) telekinesis (3/10) - ability to move objects

2) psychic energy absorption (6.7/10) - ability to absorb energy; sometimes absorbs emotions, too; adds absorbed energy to his own energy

3) psychic energy transference (6.9/10) - ability to transfer energy to others; those who he transfers his energy to do not contain his powers for long because they can't contain and control it like him; sometimes transfers emotions

4) chlorokinesis (5.8/10) - ability to manipulate and grow plants

5) spiritual awareness (4.9/10) - ability to sense energy of spirits and fellow espers

6) astral projection (3.2/10) - ability to leave physical body; can also go into bodies and minds of others, though it is uncertain if he can possess others

Personal Thoughts:

1) This power is a common one, especially since Uraraka and Inko Midoriya can do something similar.  However, I'm thinking that to make it more specific and unique, maybe the user can have the ability to draw common molecules or atoms closer to him.  For example, if he wanted to get his remote for his TV, the user could bring all the molecules or whatever that make up the remote to him.  Drawbacks would be that anything that is similar molecularly would also be brought to the user.  There is the possibility that the user could learn to control which molecules to bring to himself.  Another thing that the user could learn that would be very advanced would be learning to attract gas molecules or atoms.  For example, he could take away all the oxygen so a victim can't breath.  This is an interesting idea for interrogations or torturing.

2) This one is interesting.  It can be deadly because if the user removes enough energy, the victim could die.  This is a very powerful ability, so one weakness idea could be that the user can only hold a certain amount of energy, so overfilling with energy could make his body collapse or fail to function or something.

3) This is related to the second one.  This is similar to Recovery Girl's quirk, though this would be that the user himself is giving his own energy to someone else.  A clear weakness would be that if the user gives too much of his own energy without recharging and resting, he could die.

4) This one is like Shiozaki and Komori, though it can be any plant.  One weakness I can think of is that the user cannot control the direction in which the plant grows; the user can only control the location and the speed of growth.

5) I am not sure how to translate this ability into a quirk since this one is specific to its anime.  However, it could mean some sort of tracking and mapping quirk, like the Marauder's Map.

6) This one is pretty common, too.  One weakness observed from other story lines that use some sort of possession is the fact that the user's body does not function when the user is out of the body.  This leads into a possible weakness: if the user is out for too long, the body will not be functional when the user returns to the body.  It could be that the body can maintain itself for a little bit, but if without the soul for too long, it can't maintain itself anymore.

concept of Ajin

Power:

There are three abilities that ajins have:

1) immortality (3/10) - ability to live forever; users can be killed, but their body parts will just come back together

2) paralyzing scream (4/10) - ability to temporarily paralyze victims within a certain range by screaming

3) invisible black matter (7.8/10) - ability to create invisible beings out of black matter; these beings vary from ajin to ajin; these beings are unique to each user, including the level of obedience, strength, specialty, etc.

Personal Thoughts:

1) I don't like the idea of immortality, but it is useful.  The way this idea was used in the anime Trickster was interesting: the character who was immortal could not kill himself even if he wanted to, but when he didn't want to die, that was when he was vulnerable to death.  In other words, he lives when he doesn't want to, and he dies when he wants to.  This is an interesting psychological concept to explore if someone wants to make an OC with this quirk.

2) This is like Black Canary from the DC Universe.  In the anime, this ability was quickly counterattacked by wearing earplugs.  However, if this were to be a quirk in BNHA, then it would make more sense for this quirk to be more powerful.

3) This quirk is similar to Tokoyami's.  I don't really have much to say about it, but I think it's very interesting.  This quirk idea would be great for a hero/ villain family because each person has a different black matter being.  If you want to see some examples of the different black matter beings, then watch Ajin.

Chuya Nakahara from Bungou Stray Dogs - (8.2/10)

Power:

Chuya can manipulate gravity.  His is broader than Uraraka's because he can walk on walls, create tiny black holes, etc.  While Uraraka makes things lighter, Chuya can also make things heavier.

Personal Thoughts:

I love this ability, and it's my favorite one in Bungou Stray Dogs.  It's pretty similar to Uraraka's so I would say for quirk ideas, I would separate making things heavier from making things lighter, and I would separate the ability to walk on walls, too.  It would be super cool to see a user who has trained with this quirk for many years fight because there are so many possibilities with fighting while controlling gravity.

Shina from Akatsuki no Yona - (6.7/10)

Power:

Shina can paralyze people and give them hallucinations when they look into his eyes.  He's basically like Medusa.  His eyesight is incredible, as well, and he can see very far away.  He has no control over his ability, so he wears a mask so that people don't look into his eyes.

Personal Thoughts:

This may not be a very original ability, but I think it has a lot of potential because a lot of people who lack one of their five senses have sharper senses than the average person due to the fact that they have one less sense to rely on.  Therefore, a user could develop some insanely good reflexes and fighting skills.  Good character development would be learning to control the ability.

Bonus - ideas I've seen online or things I came up with:

► groundhog day (9.4/10) - ability to redo a certain amount of time; usually it's a redo of the last 24 hours, but you can decide whatever; there is also the option of this ability being triggered every time the user dies; if it is the case that the ability is triggered every time the user dies, it would be a good psychological story concept because if comrades know the power and notice that the user starts sounding robotic with responses, it can be a scary thought knowing that the user probably died several times already

► ability to see level of power of someone on a scale from 1-10 (8.5/10) - this isn't really a fighting quirk, but who said that the only allowed quirks are the fighting ones?

► ability to see time of death of others (7.9/10) - the time of death isn't permanent since it is in the future, so the user could monitor people's actions to make sure people don't suddenly die

► chicken magnet (10/10) - not a fighting quirk, but this would be hilarious

► red strings of fate (5/10) - not a fighting quirk, but imagine being able to bring people together and allowing them to meet people they deserve to meet; how kind