I can think of two I'd consider essential:

isthereanydeal.com
Lists game deals and freebies of numerous digital game stores, as well as bundle and pricing history. Constantly updated.

https://www.pcgamingwiki.com/wiki/Home
"PCGamingWiki aims to list fixes and workarounds for every single PC game"

Any game subreddit, those are always chock full of information and active no matter how old a game is.

The Cutting Room Floor, a wiki of cut content and other things.

Open Source Game Clones; why pay 60 bucks for a shooter game when you'll get more value out of a free game?

The Obscuritory is a fine archive of well written articles on the occasionally weird PC game and things along those lines.

Vogons, the home of DOSBOX and many important matters of old computer gaming.

Gameplay and/or Reviews - https://www.youtube.com/
Aggregate Reviews - https://www.metacritic.com/

How Long To Beat - https://howlongtobeat.com/
Speedruns - https://www.speedrun.com/

Guides - https://gamefaqs.gamespot.com/
Guides and/or Modding - https://steamcommunity.com/?subsection=guides
Modding - https://www.nexusmods.com/

PC Gaming News - https://www.pcgamer.com/news/
PC Gaming News - https://www.pcgamesn.com/
Hardware News - https://www.youtube.com/channel/UChIs72whgZI9w6d6FhwGGHA

EDIT: Metacritic uses weighted average scores that favours more prominent reviewers than simple average calculation for review scores. Would advise Darvond's suggestion of OpenCritic over MetaCritic any day.

Some may prefer OpenCritic for being more focused and less prone to userbombing.

I always thought Metacritic was doing a simple average calculation; no idea it was using weighted until now. Thank you, will be using this going forward.

https://www.mobygames.com
Anyone want to dig info for video games will need this.

First things that come to mind are:

https://www.google.com
https://www.wikipedia.org
https://pcpartpicker.com

You've literally got the wrong TLD for this; Wikipedia is a .org

You can compile a list in the first post if it's not too much trouble.
I'd like to add:

https://gg.deals/
https://www.moddb.com/

local socialization aid service

Gamepressure.com

My favourite site for gaming info.

Antimicro - https://sourceforge.net/projects/antimicro.mirror (free xpadder style controller to keyboard & mouse mapper)

AutoHotkey - https://www.autohotkey.com

Borderless Gaming - https://sourceforge.net/projects/borderless-gaming.mirror (effectively adds Borderless Windowed functionality to games that can run in "Windowed" mode but have no native Borderless Window support)

Flawless Widescreen - https://flawlesswidescreen.org (particularly useful for Ultrawide / multi-monitor owners)

GameSave Manager - https://www.gamesave-manager.com

MSI Afterburner - https://www.msi.com/Landing/afterburner/graphics-cards

Unigine (3D Benchmark) - https://benchmark.unigine.com

Widescreen Gaming Forum - https://www.wsgf.org

DRM-Free Game Lists:-
Epic - https://www.pcgamingwiki.com/wiki/List_of_DRM-free_games_on_Epic_Games_Store
Steam - https://steam.fandom.com/wiki/List_of_DRM-free_games

GPU Drivers:-
AMD - https://www.amd.com/en/support
Intel - https://downloadcenter.intel.com/product/80939/Graphics
nVidia - https://www.nvidia.com/en-gb/geforce/drivers

Linux Game Support:-
Adamhm' WINE wrappers - https://www.gog.com/forum/general/adamhms_linux_wine_wrappers_news_faq_discussion/post3
Lutris - https://lutris.net
PlayOnLinux - https://www.playonlinux.com/en

Some Walkthrough sites:-
https://www.fandom.com/topics/games
https://www.gamebanshee.com/games.html
https://guides.gamepressure.com
http://www.gameboomers.com/walkthroughs.html
http://gamesolutions.efzeven.nl/index-a-z

Universal Hint System https://www.uhs-hints.com/

To get incremental hints and not just the solution.

But maybe not this; since Fandom wikis are often polluted with ads, pop-culture garbage, and the fact checking & administration are practically nonexistant. I'd sooner start at StrategyWiki and work to the networked wikis from there.

Not to mention that since Fandom absorbed Gamepedia, many of their wikis have gone massively downhill; since Fandom is nothing more than a garbage wiki farm. The admins won't even let you leave or close an unwanted wikia.