Well, I just did a massive writeup on Bastion on this Very Board, and it's currently $3. As a personal favorite and a game with one of The Best Soundtracks in gaming, it's a good pick. Transistor is $4 and Pyre is $5, so if you've put in enough hours on Hades and want to see what else the same people made... there you go.
Thief Gold and Thief 2, two of the greatest stealth games ever made, period, bar none, are sitting at $0.97 apiece, as usual, as is Deus Ex. I recommend these games every year and don't intend to stop. The System Shock games are also great, same developer as Thief, and $2.50 each. BioShock Remastered, the spiritual successor to System Shock, is $5, so there you go on that front too.
Disco Elysium is only $15 off, sitting at $25, but if you like RPGs, and games with strong writing, and games where your choices matter, and games with good world building and strong narrative... uh... honestly that's almost a bargain for how much you'll get out of this one. And if you want to play the game that it very much seemed inspired Disco Elyisum, the legendary Planescape: Torment is only $6. As are the other Infinity Engine RPGs, so if you're into isometric realtime-with-pause games boy are there some deals for you.
Metal Gear Solid 5 is $7.50 (if you want both parts of it), and Dishonored is $6, including all the bells and whistles. Both pretty solid. Mark of the Ninja Remastered, the violent and stylish (it's kinda their thing) 2D stealth game from Klei is $8, although it's $2 if you own the original.
Alright, back to shilling retro games. Anachronox, a genuinely funny Chrono-trigger inspired RPG developed by Ion Storm, is $1 as usual, Arx Fatalis, Arkane's Ultima Underworld knockoff (and I say that lovingly, Arkane is great even if their entire existence as a game developer more or less consists of them genuflecting at Looking Glass's altar with varying degrees of subtlety), is $1.50, Command and Conquer Remastered, a lovingly-developed beautiful remake of the first two Command and Conquers in high resolution, cheesy FMVs and all, packed with extra content and one of the best soundtracks in games, proving that at least someone at EA isn't completely dispassionate and still loves RTSes, is $8, and Sega's Dreamcast collection bundle, including several very good games that nobody played on release like Jet Set Radio and Space Channel 5, arcade hits like Crazy Taxi, the rare good Saturn game NiGHTS Into Dreams, and two of the more entertainingly bad 3D Sonics in Sonic Adventure 1 and 2, is $6.
Actually, there are many good PC releases of games you might have originally ignored at launch on sale here. Icaruga, widely considered to be one of the greatest shoot-em-ups to ever exist, is $5, Killer7, the game that forever cemented Suda51's reputation as The Weird One (TM), is $8, and Strife: Veteran Edition, the re-release of the obscure FPS with RPG elements on the Doom engine, is only $2.50.
Back in the indie realm, FTL is also $2.50 and if you are one of the three people in the world who have never played FTL, I recommend you take this opportunity to rectify this, and maybe spend $7.50 picking up its successor, Into The Breach, as well. Undertale is $3, in a similar vein. And while it's a bit pricier, Stardew Valley (the best Harvest Moon game) is also on sale. Lucas Pope's astonishing Papers Please is $5, and his even better Return of the Obra Dinn is... actually only $5 off at $15. Buy it anyways.
I can hardly resist an overlooked retro classic that's also technically an indie game, and Psychonauts is $5. Psychonauts is one of the funniest, best written games ever made, and you should play it. Also the sequel's coming out soon. But if 2D platformers are more your speed, well, we've got plenty of those. OlliOlli2, the best skateboarding game that didn't pay for Tony Hawk to adorn the cover, is $3, the maddening N++ is $7.50, but if you're into hardcore platformers, Celeste is one of the very best, arguably better than N++ and far better than Super Meat Boy mechanically, and beating both of them out on a narrative level. And it's $5. For 3D platforming fans I recommend Yoo- haha, no. I recommend A Hat in Time, which is $15 and combines the irreverent humor and out-there scenarios of Paper Mario with the gameplay of Regular Mario (specifically Mario Sunshine), and then adds a hefty dose of its own personality, as well as 50-player online, split-screen co-op, and mod support. And while it's not a platformer technically, it's time to bring up one of the best games of 2004, Resident Evil 4. No, I'm of course talking about Katamari Damacy, the most adorable story ever to exist about parental abuse and casually rolling up people into balls that get turned into stars. Although when I put it like that...
Do play Resident Evil 4, though. It's $5, and I don't care if you don't like horror, because it's one of the best action games ever made. Although 2004 was wall-to-wall great games, and more of them are on sale here now. All the Half Life games except Half Life Alyx (which you probably can't play anyways) are going for a few dollars a piece, and the episodes are really good and fun and also Half Life 1 and 2 are genre-redefining smash hits that any FPS fan honestly owes it to themselves to go play. And speaking of FPS classics, Doom and Doom 2 are both 1.50, and you can pick them up alongside Final Doom and Doom 2's Master Levels for a total of $5. Not only are you buying a piece of gaming history, you're also buying a ticket that lets you access some of the best fanmade content in all of gaming: The Doom community has been at it for a very long time, and they are very, very good at what they do. And if that's not enough Doom for you, Doom 64, the classic Doom that wasn't, is $1.50, and Doom 2016, the game so good that it almost single-handedly made Doom relevant again in the mainstream, is $6. You can also pick up Doom Eternal and all its DLCs for a mere $30, which is not too shabby for a game that's only a bit over a year old.
But if you want the most gameplay time for your buck, at a killer discount, pick up Dark Souls II: Scholar of the First Sin, which is a mere $10. Is it the best Dark Souls game? Emphatically not. But Dark Souls at its worst is better than many series at their best. If you're a newcomer to the series, Dark Souls II is a fine introduction, even if it's not the best game. Although for $10 more you can pick up Dark Souls III and all its DLCs. Playing Dark Souls 1 first is honestly the best bet, but sadly that game isn't discounted at all.
Of course for those of you who like your giant action adventure games 2D, you can pick up Bloodstained: Ritual of the Night for $20. This is a metroidvania by the man who's behind the "vania" part of the, Koji Igarashi. I have heard from people who are more into the genre that it's a really good one. But if you want a cheaper one, check out the Guacamelee! games, Hollow Knight, and Axiom Verge.