According to SteamDB there are around 52,000 items on sale so it might be difficult to spot good deals all by yourself.
Use SteamDB for filtering offers according to rating, price and discount or ggdeals
https://gg.deals/deals/?store=4
but remember other stores may still beat Steam's pricing by a margin so always check if you get the best deal really. Use ITAD or gg.deals to check games you consider buying.
I also recommend the amazing Joseahfer and the list he keeps updated on SG
https://www.steamgifts.com/discussion/8OUwT/steam-the-winter-sale-2021/search?page=3#2Ha93zU
and of course post your own game findings here. I'll begin with:
Climbros 90% off HL
Ghosts of Miami 90% off HL
Grimoire : Heralds of the Winged Exemplar (V2) 90% off HL
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