Climbros 90% off HL
Ghosts of Miami 90% off HL
Grimoire : Heralds of the Winged Exemplar (V2) 90% off HL edit: already listed

A House of Many Doors -85%, historical low https://store.steampowered.com/app/437250
The Caribbean Sail -90%, historical low https://store.steampowered.com/app/657690
Aztez -90%, historical low https://store.steampowered.com/app/244750
RIOT: Civil Unrest -90%, historical low https://store.steampowered.com/app/342310

Historical low:
Totally Accurate Battle Simulator -55%
Undead Horde -72%
Whispers of a Machine -80%

https://store.steampowered.com/app/884260/Akane/ -75%

Historical low:
It Takes Two -50%
The Enchanted Cave 2 -77%
Cat Quest II -60%
Not historical low, but in my opinion a good deal
Return to Shironagasu Island -60%

https://store.steampowered.com/app/956030/Creaks/
-60% lowest ever

If you have an active Humble Choice subscription, Mirrors Edge Catalyst is even cheaper in the Humble Store right now, 1.87€ to be exact.
Yeah, its not much, a few eurocents at best, but hey, on rare occasions even this could make a difference!

https://store.steampowered.com/app/954650/Druidstone_The_Secret_of_the_Menhir_Forest/

Lowest price ever for a tactical rpg from the creators of Legends of Grimrock

I guess these two games have the lowest prices again.

Halfway
https://store.steampowered.com/app/253150/Halfway/
Samorost 3: Cosmic Edition
https://store.steampowered.com/bundle/266/Samorost_3_Cosmic_Edition/

If you are an active Humble Choice subscriber, you can get them way cheaper with an additional 20% off on Humble Store, too.
Plus, they both come with Steam keys and downloadable DRM-free versions as well.

Historical low prices (Most of the games):

Anniversary Collection Arcade Classics - https://store.steampowered.com/app/1018000/Anniversary_Collection_Arcade_Classics/ - 80%
Break the Game - https://store.steampowered.com/app/739540/Break_the_Game/ - 90%
Castlevania Anniversary Collection - https://store.steampowered.com/app/1018010/Castlevania_Anniversary_Collection/ - 80%
Contra Anniversary Collection - https://store.steampowered.com/app/1018020/Contra_Anniversary_Collection/ - 80%
Daymare: 1998 - https://store.steampowered.com/app/842100/Daymare_1998/ - 80%
Erica - https://store.steampowered.com/app/1514930/Erica/ - 80%
Formata - https://store.steampowered.com/app/580040/Formata/ - 90%
Hand of Fate 2 - https://store.steampowered.com/app/456670/Hand_of_Fate_2 - 80%
Hellbound - https://store.steampowered.com/app/753590/Hellbound/ - 75%
Little Triangle - https://store.steampowered.com/app/575050/Little_Triangle/ - 73%
Rebel Galaxy Outlaw - https://store.steampowered.com/app/910830/Rebel_Galaxy_Outlaw/ - 80%
Shakedown: Hawaii - https://store.steampowered.com/app/598730/Shakedown_Hawaii/ - 75%
Stranded Sails - Explorers of the Cursed Islands - https://store.steampowered.com/app/943260/Stranded_Sails__Explorers_of_the_Cursed_Islands/ - 80%
The TakeOver - https://store.steampowered.com/app/418620/The_TakeOver/ - 75%
ZONE OF THE ENDERS The 2nd Runner: M∀RS - https://store.steampowered.com/app/650510/ZONE_OF_THE_ENDERS_THE_2nd_RUNNER__MRS/ - 80%

No EA Games?

Maid of Sker now costs 14.99€ (-40%) The bigger discount ended with the begin os the Steam Sale.

Vignettes -50%
Progressbar95 -50%
SuperMash -90%

Hustle Cat -90%, historical low https://store.steampowered.com/app/453340
CROSSBOW: Bloodnight -67% https://store.steampowered.com/app/1329540
Thunder Wolves -90%, historical low https://store.steampowered.com/app/232970
Mini Motor Racing X -90%, historical low https://store.steampowered.com/app/1303990
Alien Squatter -90%, historical low https://store.steampowered.com/app/1131750
Mainlining -90%, historical low https://store.steampowered.com/app/454950

The Sims 3 collection -82 % https://store.steampowered.com/bundle/1247/The_Sims_3_Collection/

its pretty hiden not showing on The Sims 3 page.

https://store.steampowered.com/app/928390/RType_Dimensions_EX/ -50% (HL)

Lost Lands: The Wanderer, -65%, historical low ---> https://store.steampowered.com/app/626640/
Milo and the Magpies, -50%, historical low ---> https://store.steampowered.com/app/1407420/
New York Mysteries: The Lantern of Souls, -65%, historical low ---> https://store.steampowered.com/app/511140/
Vessels, -60%, historical low, bundled once ---> https://store.steampowered.com/app/1371330/

Dream Cycle -50% (HL)

Bah, I forgot to get my free card from the queue yesterday. At least the sticker reset is every other day though.

Miles & Kilo 90% off HL
Obsurity 90% off HL

Prince of Persia bundle is 82% off, costing only 8.95.

Wandersong is 75% off, making it historical low https://store.steampowered.com/app/530320/Wandersong/

PIXELJUNK™ MONSTERS ULTIMATE + SHOOTER BUNDLE https://store.steampowered.com/sub/34096/

Obsideo (a Phasmophobia-like) is a record 40% off right now. https://store.steampowered.com/app/1708460/Obsideo/

nothing new. I cant see me buying any of games 'just because its on winter sale', cause i got same prices everytime there is a sale...i wanted to buy dishonored 2+doto bundle, but its only -80, while it was even -85...