Characters:

-Trajann Valoris: the old man is still amazing, arguably better than he was in 9th edition. When he leads a unit they can ignore all negative modifiers (except to their armor save) and he still slaps in melee. What makes him an auto include in my opinion is the Moment Shackle, which gives him the ability to make him and his unit fight first (the other two abilities of the moment shackle are nice, but fight first is so powerful that you are mostly going to pick fight first) which is just bonkers good.
-Valerian: if Valerian leads a unit, enemy units get -1 AP on their weapons in the fight phase, he also has decent melee. Valerian is good, but unfortunately for him we are really spoiled for choice in 10th regarding characters, so I believe he won't see as much play because there are just stronger options in our index.
-Aleya: Valerians BFF and certified badass. She's even better in 10th. She has great melee, she gives Fight First to the squad she leads and gives her squad +1 to hit if they are below starting strength. The problem is that unfortunately the squads she can lead are not that good and/or overshadowed by other options.

-Shield Captain: All three Shield Captain variants provide value because they let you use one stratagem for free once per battle round, even if that strat has already been used, which is a very powerful ability. That being said the standard Shield Captain was rarely played in previous editions. He was never a bad unit, but simply overshadowed by better options...well, no more! The Shield Captain is really good in 10th because he let's his unit use two Katahs instead of one in the fight phase and once per game lets his unit use all three Katahs at the same time.
-Allarus Shield Captain: the Terminator Captain is still good. He also has access to the aforementioned ability to make one strat per battle round free, which is great. He can also fight on death on a 2+ if he hasn't already fought. Not bad, but the standard Shield Captain provides more value in my opinion.
-Shield Captain on Dawneagle Jetbike: the infamous bike captain is in a weird spot in 10th edition. In a vacuum his rules are great. He also lets you use one strat for free each battle round and he and his unit can consolidate 6" instead of 3" which is always good. He also lets you fall back at the end of the fight phase once per game or lets you make a normal move at the end of the fight phase if you are not within engagement range which is amazing.....it's just that in these scenarios he would be leading a unit of jetbikes....and jetbikes are not that great in 10th.
-Blade Champion: The Blade Champ got introduced in 9th ed and was a premium beatstick, but was ultimately overshadowed by other characters that were better force multipliers. In 10th he i very much worth including in most lists because once per game he and the unit he is leading can advance and charge, which is just such a valuable ability for a mostly foot slogging army like Custodes. He is also still very powerful in melee and a prime candidate to lead a big unit of Custodian Guard, because like all characters leading a unit he also benefits from their ability to re-roll all wounds on an objective you control, which is hilarious with his dmg3 devastating wounds profile. If you roll hot, he can chuck out a ridiculous amount of mortal wounds.
-Knight Centuria: makes sisters unit faster and charge better...not bad like Aleya, it's just that Sisters are not that impressive in 10th.

Troops:

-Custodian Guard: Custodian Guard are one of the strongest units in our Index. They always re-roll 1s to wound and if you are on an objective you control, they re-roll all wounds, which is amazing. They can also double shoot once per game, which makes them surprisingly deadly in ranged combat also.
-Prosecutors: Still a cheap backline unit for holding objectives, honestly won't do much else.
Sagittarum Custodes: : The Sagittarum are still good in my opinion, but you have to take them in units of 5 now, which is a shame because losing the option of taking a unit of 3 as a backline unit feels bad. 10th ed unit sizes strike again.
They have a neat synergy with the Coronus: Sagittarum can get Devastating Wounds on their Bolters once per game and the Coronus lets a unit that just disembarket re-roll all wounds in the shooting phase. It's cute, but probably not worth the investment in light of better options.

Elites:

-Wardens: Oh boy...Wardens got quite the glow up in 10th. They were already a really good unit in 9th edition, but their new Living Fortress ability takes them over the top in 10th...they can get a 4+ Feelnopain once per battle, which basically makes them an immovable object for one phase. They are also -1 to be wounded if a character is leading the unit (which is always going to be the case) and if they are targeted with an attack with higher strength than their toughness as a cherry on top. Wardens are going to find a place in most Custodes lists.
-Venerable Contemptor Dreadnought: Still ugly but now an actual option. It's really tough due to its unyielding ancient ability, which lets the Contemptor get back up on a 2+ with D6 wounds after being destroyed the first time.
-Allarus Terminators: T7 Custodes in shiny Terminator Armor? Yes, please! Allarus Terminators are awsome in 10th. They are tough, they re-roll all failed wounds against vehicles, monsters and characters. Also their "From golden Light" ability gives them good mobility for mission play. Great unit.
-Vigilators: Badass Sisters with badass Swords. They actually have good melee, but our Custodes units do melee even better.

Forgeworld:
-Contemptor Galatus Dreadnought: still the coolest looking drednought in the game. Unfortunately all Forgeworld dreads suffered a nerf to their movement from 9" to 6" which is a massive nerf for a dreadnought that does nothing than melee. If you manage to get the Galatus into melee, it's going to do work and be a major headache for your opponent since the Galatus Shield now provides -1 to wound in the fight phase for enemy units, which makes the Galatus extremely tough in melee.
-Contemptor Achillus Dreadnought: the second coolest looking dreadnought in the game, but it suffers from the same problem as the Galatus. The movement nerf is brutal on these two dreads. The Achillus still does a lot of dmg in melee and now also can dish out mortal wounds after making a charge, which is great if you manage to actually get it there.
-Aquilon Terminators: still the most chonky Terminators in town, but they really took a hit in 10th. They can re-roll failed wound rolls of 1 if they are shooting the nearest enemy unit, which is nice I guess, but their melee weapon options really took a nerf compared to 9th, especially the power fist. They are also more expensive per model than Allarus Terminators, which are just better anyway.

Fast Attack:

-Vertus Praetors: well....they can't be good all the time, right? Our infamous dawneagle jetbikes have always been a powerful unit, but they really took a dive in 10th. They are not as tough as terminators, salvo launchers don't do as much damage as before and struggle to wound vehicles and they are expensive at 90 points per model. They still get +1 to wound on the charge and can do mortal wounds when moving across enemy units, but ultimately they are overcosted for what they do in my opinion.
-Witchseekers: Sisters with flamers that force battle shock tests.


Forgeworld:
-Venatari: They can fall back and charge now, which is good, but their pistols are only dmg1 now and they cost 235 for three dudes, that's too expensive for what they do in my opinion. Also the lances option went from S6 to S4 on their shooting profile for some reason.
-Agamatus Jetbikes: Similar issues as the standard Vertus Praetors. Not T7 for some reason, expensive and don't hit as hard as other options we have access to.

Heavy Support:
-Venerable Land Raider: it's actually not bad now, which is kinda baffling after such a long time in dumpster tier. It's rather tough, provides some anti tank firepower and has assault ramp. It also gets the Martial Katah rule, which means our Land Raiders know Karate.

Forgeworld:
-Telemon Heavy Dreadnought: Oh how the mighty have fallen. The Telemon is not much tougher than a venerable contemptor, if you play him with double fists you get no additional benefits in melee because you can only attack with one of them which is just stupid and the firepower if just OK.
-Caladius Grav-Tank: Best value anti tank firepower we have access to. Amazing unit and is going to see a lot of play for sure.


Flyer:

Forgeworld:
-Orion Dropship: proof that custodes truly have the most pimped up rides in the imperium. Still very expensive and if you use it for transporting troops and/or a dreanought its basically the definition of "all eggs in one basket".
-Ares Gunship: provides the heaviest anti-tank firepower custodes have access to. Probably still too expensive.


Dedicated Transport:

-Anathema Psykana Rhino: Sisters are not that great in 10th, but if you are hellbent on playing them, some Vigilators with Aleya in a Rhino might be nice.
Forgeworld:
-Coronus Grav-Carrier: I still want to love the Coronus, but I am not sure if it's going to find a place in any list.

-Inspirational Exemplar: bearer has a leadership of 5+ and can un-battle shock one unit once per game. Not bad
-Veiled Blade: +2 attacks and once per game triple the OC of the bearer. Great choice for the Blade Champ.
-Ceaseless Hunter: bearers unit can fall back and charge and once per game can move up to 6" if enemy unit ends normal move, advance or fall back within 9". Strongest ability of the four enhancement options by far.
-Unstoppable Destroyer: Mortal wounds on the charge and can force battle shock tests. Not bad, but Veiled Blade and Ceaseless Hunter are just far better.

S-Tier: you are going to use these in every single game
A-Tier: Very strong stragems
B-Tier: Situationally useful
C-Tier: Not that good

-Arcane Genetic Alchemy: -1 dmg on enemy attacks for 2CP. This is extremely powerful on Custodes bodies and you are going to use this in most of your games.
-Unwavering Sentinels: gives your unit fight first if it is within range of an objective marker. This is probably one of the most powerful stratagems in the game and one of the reasons Custodes are one of the most powerful, if not the most powerful melee army currently.
-Slayers of Nightmares: +1 to wound against vehicles or monsters in the fight phase. Great value in 10th with the overall increase in toughness.
-Vigil Unending: bring back one destroyed Custodes model (can only use this once per unit). Bringing back things like an Allarus Terminator with this strat is just amazing value.
-Sworn Guardians: one objective you control becomes sticky. Great strat for a low unit count army like Custodes
-Avenge the Fallen: +1 Attack when under starting strength +2 attacks instead when under half strength. Extra attacks are always powerful on high quality profiles like Custodes, but maybe a bit more situational than the other options. Still a good strat to have.

Not a single bad strat among these and some of the most powerful ones in the game.