WINTER SALE 2019 - Good games under (Or around) one buck

ReThink 1.49
The Incredible Adventures of Van Helsing 1.49 (Same for every other game in the franchise)
Chyper 1.49
Kane and Lynch Colection 1.31
Teslagrad 0.99
Defunct 0.99
ROOT 0.99
Not Dying Today 0.99
Crash Time 2 0.88 & Crash Time 3 0.99
Just Cause 0.97 & Just Cause 2 1.49
Spirits of Xanadu 0.79
Disoriented 0.71
Tomb Raider some older versions are under 1

Interesting story based walking simulator Virgina is $0.99
https://store.steampowered.com/app/374030/Virginia/

I can vouch for some of the ones in the list as being great small games, or simply not so small but ATM at big discount giving lots of fun for ~$1: Superflight, Marble Race, Penumbra, Dex for example. These are some that were in my selection just yesterday, but now only Creeper World is going to be purchased with my meager wallet (xmas gift):
https://store.steampowered.com/app/391170/Void_Invaders/
https://store.steampowered.com/app/368570/Beat_Da_Beat/
https://store.steampowered.com/bundle/8879/Space_Hole_2016__2018/
https://store.steampowered.com/app/1114430/Ballex/
https://store.steampowered.com/app/15210/Silent_Hunter_III/
https://store.steampowered.com/app/422910/Creeper_World_Anniversary_Edition/

My wishlist has many more, but those are the best I think. You could add Breach & Clear to there. Rest of games I could list here are already in your list.

Ones that I've played and could recommend since I enjoyed them

Platformers

https://store.steampowered.com/app/96100/Defy_Gravity_Extended/ (currently $0.49)

https://store.steampowered.com/app/563180/Dispersio/ (currently $0.49)

https://store.steampowered.com/app/917290/Duck_Souls/ (currently $1.39)

https://store.steampowered.com/app/463220/Dungeon_of_Zolthan/ (currently $0.49)

https://store.steampowered.com/app/726510/Heads_Run/ (currently $1.34)

https://store.steampowered.com/app/453830/Innoquous_5/ (currently $0.49)

https://store.steampowered.com/app/269270/LOVE/ ($0.74 , but I'd recommend the sequel kuso over this since it contains this too, though at $2.49 kuso is out of range of this topic)

https://store.steampowered.com/app/969130/The_Lost_Soul/ (currently $0.67)

https://store.steampowered.com/app/516480/Pinkman/ ($0.79)

Puzzle (sadly I don't play much of these cause I'm bad and therefore can't recommend much)

https://store.steampowered.com/app/725080/Fearful_Symmetry__The_Cursed_Prince/ ($0.99)

Role Playing (sadly not much here because I haven't played much in the way of cheap ones)

https://store.steampowered.com/app/107310/Cthulhu_Saves_the_World/ ($0.89 , also comes with Breath of Death VII)

Roguelike

https://store.steampowered.com/app/547980/Equin_The_Lantern/ ($1.24, other games by the dev look interesting too, but I haven't played those)

Shooters

https://store.steampowered.com/app/285440/Crimzon_Clover_WORLD_IGNITION/ ($1.99 which is basically the cutoff for this, but it has a lot of challenge and replay value)

https://store.steampowered.com/app/367140/Wish_Project/ ($1.99 base price though, and not sure if I've ever seen this actually go on sale)

https://store.steampowered.com/app/555710/Zolg/ ($0.49)

My store's in CAD, but I'll assume anything ~$2.25 and under counts. Does mean I won't include prices myself, though, since they'd just be misleading.

From my wishlist:

Starman
EMMA: The Story
SanctuaryRPG: Black Edition
Golem Creation Kit
Pale Echoes
Immortal Defence
Goats on a Bridge
Gunman Clive
Killing Time at Lightspeed
Shu
LIBRARY
Universally Loved
Kensho
Little Big Adventure 2
Three Fourths Home
The Great Voyage
Downwell
Letter Quest: Grimm's Journey Remastered
Spell Casting: Meowgically Enhanced Edition
Alicemare
6180 the Moon
Grandpa's Table
Incredipede
Cheap Golf
1979 Revolution: Black Friday
Spitkiss
The Night of the Rabbit
Claire
Last Word
Legacy of Dorn: Herald of Oblivion
Murasaki
One Small Fire at a Time
Sabres of Infinity
Tardy
Recursed

I am the master of cheap gaming. It's me.

Look here for games under $1
https://gg.deals/deals/?drm=1&maxPrice=1&onlyBestDeal=1&onlyHistoricalLow=1
Here for under $2
https://gg.deals/deals/?drm=1&maxPrice=2&onlyBestDeal=1&onlyHistoricalLow=1

https://store.steampowered.com/app/234900/Anodyne/ $0.99 . Heard great things. Going to buy it myself soon.

https://store.steampowered.com/app/461340/A_Timely_Intervention/ $0.99 Seems decent.

Goblins and Coins - $0.99

Deus Ex: Game of the Year Edition classic, one of the best of It's time!
PORTAL BUNDLE The Best., really great deal
PAKO 2 Nice arcade

Can't recommend Bad Rats as it is not on sale :(

My store's in Euro, but here's a list: (Some of these have probably already been mentioned.)

Below €1
Refunct 0,89€ - Casual first person 3D platform puzzler.
Superflight 0,74€ - Procedurally generated wingsuit flying sim.
Zenge 0,69€ - Beautiful casual puzzle game.
Hook 0,66€ - Minimalist puzzle game.
klocki 0,74€ - Casual puzzle game. Same dev as the above two.
Blueprint Tycoon 0,74€ - Production based management sim.
BalanCity 0,79€ - casual puzzle city builder/balance physics game.
Penumbra Collectors Pack 0,99€ - Includes both Penumbra Overture and Penumbra Black Plague Gold Edition. First person horror puzzle, it's a classic.
Silence of the Sleep 0,67€ - sidescrolling psychological horror adventure about a man who has lost his memory.
AntVentor 0,99€ - Point & Click adventure
Sandmade 0,55€ - Casual puzzle game about matching blocks to make shapes.
Almost There: The Platformer 0,81€ - Unforgiving hardcore platformer with a nice art style.
Acid Spy 0,99€ - Cyberpunk first person stealth action run&platform game, with an arena-fps feeling. The movement system is quite something.
Defy Gravity Extended 0,39€ - a mix between classic platforming and gravity based puzzle solving.
Mind Spheres 0,39€ - A neon cyberpunkish mix between physics puzzle and minigolf/pinball.
Deep Blue 3D Maze in Space 0,50€ - 3D platformer about a rolling ball in space.
Quantum Conundrum 0,98€ - Portal style 3D puzzle platformer
Caravan 0,99€ - Trading simulator

Everyone should already own these, but the classic Valve titles are almost all below €1. See this collection for full list. Portal, Portal 2, Left 4 Dead, Half Life 2, etc...

€1 to €1,99:
Flood of Light 1,80€ - 2D puzzler with a beautifully drawn art style.The soundtrack is also very good.
Pinstripe 1,49€ - Atmospheric indie adventure game with a serious story.
Valley 1,99€ - First person adventure where you race around in a suit that "grants exceptional speed and agility along with the phenomenal ability to manipulate the life and death of all living things. "
The Mooseman 1,74€ - 2D indie adventure based on finno-ugric culture of bygone pagan times.
Shiny 1,49€ - Non-violent 3D scifi sidescrolling platformer about a little robot trying to rescue his friends.
Grow Home 1,99€ - Charming climbing open world adventure about a little robot that grows plants to reach his spaceship. (Says works best with a controller, but is also fine with a mouse&keyboard)
Hidden Paws 1,79€ - Adorable game about finding hidden cats.
Distrust: Polar Survival 1,79€ - Procedurally generated horror isometric survival adventure set on an arctic research station.
Good Robot 1,84€ - Scifi roguelike shoot-em-up.
Bastion 1,87€ - Handpainted action based RPG.
Seraph 1,94€ - 2D acrobatic shooter/platformer.
The Purring Quest 1,29€ - Funny platformer where you play as a cat on a quest.
Valhalla Hills 1,49€ - Strategy building sim with a puzzle element set in the Viking era.

Some classics:
Divinity II: Developer's Cut 1,99€ - Open world RPG set in the Divinity universe. This game came before Original Sin, and is a fantasic RPG with some very unique elements. (Spoilers; )) Perhaps one of the most criminally overlooked RPG's of this era, and if you like RPG's, give it a shot. (Used to be called Divinity II Ego Draconis, and later The Dragon Knight Saga.)
Amnesia: The Dark Descent 1,99€ - First person horror, absolute classic.
The Witcher: Enhanced Edition Director's Cut 1,19€ - It's The first Witcher, what more needs to be said? ;)
Overlord 1,24€ - RPG about being the villain and controlling an army of minions. Very hilarious, and an absolute classic.
Cosmo's Cosmic Adventure 1,99€ - DOSbox game, one of the best platformers of the 1990's.

Like every other sale, the original Thief games are all under 1€. The "new" Thief (2014) is massively discounted as well.
Don't Open the Doors is and interesting and perhaps little-known game that's currently 1.09€.

Also, the DLCs for Friday the 13th: Killer Puzzle are all under 1€ if you played that (if you haven't, then you definitely should by the way) :)

https://store.steampowered.com/developer/KuKo - all games on sale

Super Panda Adventures 75% off - $1.24

How To Date A Magical Girl 90% off - $0.89 - Historically Lowest Discount.

Ultimate Space Commando - 90% off
Looks pretty good.

Here's a bit of a playthrough:
https://www.youtube.com/watch?v=DFy5h1Z42CA

Her Story - $0.99
The Miskatonic - $0.59
Red Comrades Save the Galaxy: Reloaded - $1.19
Leviathan: The Last Day of the Decade - $1.49
The Room - $1.24
Slender: The Arrival - $0.99

Arx Fatalis - $1.49
After reading the list I bought Bleed(0,84€)+A Robot Named Fight(1,02€) and The Legacy of Kain Collection on GMG for 3,04€ 🙂. My backlog is thankful.