I've got a few home rules I've used for years.

1. Healing Potions: Drinking is a bonus action, using an action player gets the max value. Potion can be thrown 15 ft to a downed target as a bonus action, DC 10 DEX check, brings target to 1 HP. Thrower can choose to spend an action to throw the potion, then they have to pass a DC 12+1 DEX for every 5 ft from target, but if they pass target can roll the healing.

2. Team inspiration: Group shares a pool of inspiration. Up to a max of 5 that can be used at anytime.

3. Inspired saving throws: Players can spend their reaction and a point of inspiration to gain a saving throw re-roll.

4. Initiative Swap: Allow the players to swap initiative rolls with one another before combat starts. Sometimes players have an idea that requires teamwork based on a specific order they’d like to act in, and this allows them to always get the order they want.

Additional smaller rules:

A) Anything you can do.... can be done to you.

B) Roleplay can give modifiers to any roll, or can negate critical hits/success.

C) Every interaction is a chance to roleplay.

D) Once combat begins, diplomacy becomes much harder.

E) When leveling Up, Players can roll or take the average HP, whichever is larger.

F) At Player level 1, Player can take a feat.

G) Caster can spend 2+1 hit dice to recover 1 spell slot up to lvl 3 during a short rest. Can gain additional level for an added hit die per level up to 5th.

I use the onednd inspiration gained from nat 1 and only lasting a day.

I am currently trying the xp to level 3 unconscious rules and its going decently. I had to change it a bit, but it allows players to do actions even at 0 hp for a price. Hard to test since they are over level 12 and they are hard to hurt.

If you drink a healing potion outside of combat its full effect.

Bottled inspirations. They get one in their inventory if they still have one.

Present players play abseetees and get xp as a reward, so I dont redo encounters 10 minutes before the start.

I've got a few.

1: Massive damage cannot result in instant death. With the exception of fall damage, I can't see a reason that I'd ever want to do this to the players, and even with fall damage, players become unlikely to die from this as soon as they have an average of 35 hitpoints. If I have traps or monsters dealing enough damage to kill instantly, then I've misbalanced my game.

2: Similarly, monsters can't crit, however some monsters will now have new features that allow them to crit, some of which may have expanded crit ranges or inflict a condition on a crit instead, although you can presume a monster can't crit by default.

3: There is no heroic inspiration at all. PCs are already powerful and features like bardic inspiration or the help action already allow PCs to reward eachother.
However I'm interested in an idea which is players just voluntarily taking "momentum tokens" any time they feel like the flow of the session isn't in their favour, this could be from a bad spat of missing or fromcthe DM disallowing a broken combo or anything really. Players can then communally spend the tokens to increment a d6 in the middle of the table (1 token to put it down on the table on 1, 2 tokens to increment it to 2, etc to a max of 6), whenever any creature makes an attack roll or uncontested ability check, they add the value on the die to their roll, however if they're a PC, they add it to all 20 rolls. This means all creatures become more likely to cause their stuff to happen, basically. The big downside is that players can just award themselves tokens at their own volition, which is easily abusable, plus they may get used to a high momentum in a session where they have a +5 or +6 and then feel that the next session has less momentum (the 6d resets by session), and award themselves more tokens. Also if they use the tokens as frustration tokens, it may hurt my feelings. But I like the idea so I continue to workshop it.

4: I use the 2024 rules for exhaustion, unless via the sickening radiance spell.

5: If you are hit by an attack while in death saving throws, you don't automatically fail any, but instead instantly make another death saving throw, still failing on 1-9 but not gaining a success on 10-20. This actually increases tension because I'm more keen to actually hit PCs when down.

Those are the big changes, I do have a few other though,

I don't allow any of the "conjure x" spells, and generally wanna look over any features that add creatures to combat to save time in combat. The summon spells in Tasha's are good, as are most class feature that add creatures to combat, and find familiar.

I don't allow silvery barbs. Not just do I feel it's too strong, I also feel that it's flavourless and entirely interested in altering mechanics that are an abstraction of the storytelling.

I don't allow the lucky feat, however I have a custom feat called borrowed luck, it works the same but if you are reduced to 0 hitpoints, you instantly fail a number of death saves equal to the number of luck points you've spent that long rest.

I have a few bits of race lore such as much fewer races having darkvision but dwarves having access to the light cantrip (and other minor benefits) and a few minor stuff like that, nothing too exciting there.