Fiendish Freddy's Big Top o' Fun free on GOG front page.

Planet of Lana - Goodie Pack is free on GOG until May 25, 1PM UTC.

Epic Games:

Fallout: New Vegas Ultimate Edition - Link

One of the best fallout games, part of the classic post nuclear roleplaying series!
You create your character, leveling each attribute and explore the nuclear post apocalyptic world
Welcome to Mojave Wasteland, the colossal Hoover Dam, and the neon drenched Vegas Strip
You’ll be introduced to a colorful cast of characters, power-hungry factions, special weapons, mutated creatures!

Are you ready for New Vegas?
Whether you’re a seasoned explorer of the Mojave or playing the game for the first time, you’ll find there are more friends and enemies to make, more consequences to your actions and more opportunities to live in glory or infamy throughout the Wasteland. The choices you make will be as crucial to your survival as ever.

Fallout: New Vegas Ultimate Edition includes:
Dead Money, Honest Hearts, Old World Blues, and Lonesome Road DLC.
Unique weapons, ammo types and recipes from Courier’s Stash and Gun Runners Arsenal DLC.

Features single player only.

Other ongoing giveaways:
none

Next time: Mystery Game Tomorrow

Warhammer Gladius is free on Steam
https://store.steampowered.com/app/489630/Warhammer_40000_Gladius__Relics_of_War/

TGV Voyages Train Simulator
Hue

Empire of Empires on indiegala

System Shock Goodie Pack is free on GOG until June 2nd, 3 PM UTC.

Tuk Tuk Extreme simulator on Indiegala
https://freebies.indiegala.com/tuk-tuk-extreme-simulator
Secret of Stormlot 1 & 2
https://sonix.indiegala.com/secret-of-stormlot
https://sonix.indiegala.com/secret-of-stormlot-2

Epic Games:

Midnight Ghost Hunt - Link

MIDNIGHT GHOST HUNT IS A GHOSTLY MULTIPLAYER HIDE-AND-SEEK GAME!

Lying in wait across a series of cursed locations, relentless spirits stalk the halls. Assigned to eliminate them are the Ghost Hunters, armed to the teeth with the ghoul-busting tech to banish them to another realm! Play both Ghost and Hunter in a chaotic 4v4 struggle between the living and the dead.

Features multiplayer only.

Other ongoing giveaways:
World of Warships x Popeye: Free Pack
Train Sim World 3 LGV Mediterranee: Marseille - Avignon
Fortnite: Coldest Circles Quest Pack
Discord Nitro Free Month

Next time: Mystery Game Tomorrow

Edit: Fixed accented letters in hyperlinks that the forum can't display properly

Deep Despair 2 on IndieGala
https://freebies.indiegala.com/deep-despair-2

Tell me Why for Xbox or Windows 10
https://www.xbox.com/en-US/games/tell-me-why
also on Steam for Windows
https://store.steampowered.com/app/1180660/Tell_Me_Why/

Steam:

Field of Glory II - Link

Field of Glory II is a turn-based tactical game set during the Rise of Rome from 280 BC to 25 BC

The game that brought the fun and excitement of the tabletop experience to digital form is back. Developed by legendary designer Richard Bodley Scott in a completely new 3D engine, Field of Glory is ready to set new standards in computer wargaming.

Field of Glory II allows you to fight large or small battles for or against Rome, or between the other nations who are as yet unaware of the Roman threat, or what-if battles between nations that never actual came into conflict historically, but might have done if the course of history had been different.

Amnesia: A Machine For Pigs can be claimed from GOG's front page for the next 3 days.

Epic Games:

Payday 2 - Link

PAYDAY 2 is a popular, action-packed, four-player co-op shooter
Players don the masks of the infamous Payday Gang as they descend on Washington DC for an epic crime spree.
Rob Banks, Get Paid – Players must choose their crew carefully
Choose Your Skills – As players progress they can invest in any of five special Skill Trees:
Mastermind, Enforcer, Ghost, Technician and Fugitive.

Features multiplayer, single player and co-op.

Other ongoing giveaways:
PAYDAY 2: The Official Soundtrack
PAYDAY 2: A Merry Payday Christmas Soundtrack
Rocket league - Battle Bus Titanium White

Next time: Guacamelee! 2 and Guacamelee! Super Turbo Championship Edition

Complementing the previous post, I'd like to inform that PAYDAY 2: The B-Sides Soundtrack is also free at the moment.

Sunblaze is free on GOG until June 14th, 10 PM UTC.