MTG Salvation

It's good in aggro decks that skew towards tempo, so mostly Izzet.
It's also good in Gruul combat trick-based decks, as you can surprise your opponent.
Boros equipments/auras also runs it, occasionally.
Also, it has haste, making the clock just that little bit faster.

Esper would definitely be control or combo with a lot of artifacts, often with a lockdown element.

Bant I would assume something with lots of enters the battlefield, and often tempo-y.

I play the Karoos and, generally speaking, I like them. They have enough tiny little synergies in my cube that they are fun to play with. Things like turning on a Land Tax whilst still making a landdrop, or untapping it with Kiora, Behemoth Beckoner or resetting a Vivid are all fun little things that makes me want to keep them for at least the foreseeable future.

I agree with Phitt here, Curse of Shallow Graves (and Disturbance) make it so that your aggro deck can keep attacking whilst continuously retaining its boardstate. You only need 1 guy to start creating an army.

As for Throne of Eldraine, I think I am most excited about Syr Konrad, he seems solid.

Also, some errata's on the peasant front: Vampire Sovereign, Vampire Aristocrat and Vampire Noble are now nobles in addition to their other creature types. I imagine this is irrelevant for most people, but it does boost Valiant Changeling ever so slightly.

Dovin has been solid for me in decks with multiple Planeswalkers, or the more prison-y UWx decks.

That curse seems good in Nekusar.

Chainer is pretty cool, too.

Another card that has been great for me in Windgrace is Jokulhaups, since it is basically an Obliterate without the uncounterability. However, you run Boseiju, Who Shelters All for uncounterability.

EDIT: Didn't read the thread well enough, you cut them already, lol.

EDIT2: Tireless Tracker is a card that is great with Windgrace, too.
A good win condition for Windgrace is also the Dark Depths and Thespian's Stage combo.
Valakut, the Molten Pinnacle and Prismatic Omen can do work, too when combined with Scapeshift or Splendid Reclamation.

Phyrexian Tower and Urborg, Tomb of Yawgmoth are pretty solid here, too, I think.

On Spectral Sailor: I think I'll be running it, but I'm also still running Phantasmal Bear, and that only sees (marginal) play in blue-based aggro decks. However, most of my blue aggro decks no longer care for the bear. They want either flyers or creatures that provide value lategame. I think this is a pretty good insurance policy late. My skies decks tend to operate at instant speed (Midnight Haunting and Thunderclap Wyvern), and this supports that. It's also pretty good in a counterspell shell for control, and I foresee it having nice synergy with Wilderness Reclamation.

Tomebound Lich this seems similar to Shadowmage Infiltrator. I am leaning towards the Lich, however, because I feel Fear is pretty easily blockable (I run a high amount of manafix, so splashing is easy and black is often splashed into), and I think looting provides more interesting decisions, and also potential upside in reanimator, a deck my drafters enjoy very much. Being a deathtoucher means it can also serve as a good blocker, and the lifegain is helpful, too, with all the lifeloss going on in black.

I like Cryptic Caves a lot, it being good flood insurance. Horizon Canopy is a card most rare cubes run I think, and this is sort of similar.

I actually like Ironroot Warlord. It has a pretty big butt, and it'll usually be 2/5-3/5 when it's cast, with the potential for more if you play a couple of Nest Invaders or such.

Valiant Changeling

I think this card is really good. It's probably realistic to be able to drop this turn 4, which is the same as Scrapper Champion, with the potential for more. Imagine going Dryad Militant, Gust Walker. That's a 3/3 double strike on turn three, and not even in a very magical Christmas land-y scenario. It also has pretty good synergy with all the incidental tribal stuff like Blood-chin Rager or Cenn's Tactician. Really cool card.

I like the splice spell. It basically gives all your instants and sorceries kicker 3w, create a 3/3, which seems like huge value to me. Imagine a Brainstorm, Lightning Bolt or something like that with this.

Mother Bear seems pretty good, too. I mean... It sorta reminds me of that Saproling spell from Dominaria in that it represents 2 or 4 power in different stages of the game.

Kasmina, Enigmatic Mentor, makes your dudes Frost Titan, makes some dudes and loots a bit. She just does so much, and fits into quite a few decks. Azorius tokens is a deck that I've been trying to push, and she slots into this quite nicely.

Tibalt, Rakish Instigator, I like it for Boros tokens, and the lifegain denial it provides can be gamewinning. Most aggro decks in my cube auto-lose against Green/White lifegain, and this circumvents that quite nicely.

Paradise Druid easy staple.

Merfolk Skydiver, just a fun card, and I like durdling. This seems better than River Hoopoe, because it pushes Simic in a more aggressive direction, which I like. It also compliments Simic's 1-drop suite quite well.

Angrath, Captain of Chaos, this is nothing amazing, but it's servicable and rounds out my hybrid slots.

Dovin, Hand of Control, being a kind of repeatable Maze of Ith against aggro is solid, and in the control mirror the tax effect should allow you to get the upper hand. Also shutting down artifact ramp is a cool bonus.

Kiora, Behemoth Reckoner, I run bouncelands, which makes this even better, and also even if you draw only 2 cards off it, it is still a Divination that ramps you a bit. Seems especially solid in a Dimir deck with big flyers. Going this into Moroii into Indulgent Tormentor into Jetting Glasskite seems good.

Saheeli, Sublime Artificer, this card seems worth it only for the passive effect already, but being able to copy a Guttersnipe, Young Pyromancer or even a Hedron Archive for a turn seems super solid and fun. Really quite unique effect, and really fun to play with I think.

EDIT: Durr, Frost Titan. Thx Leelue.

Wouldn't Grapeshot also be a solid inclusion in this list? I think being able to storm off isn't that unlikely, and as long as you target something of yours with the original copy, you get to do it all again next turn.