Metro 2033 free on steam
Metro 2033 is the first installment in the franchise. This game available at really low prices already, but now it is an opportunity for you to obtain a copy for free. Steam currently has a weekend deal for all Metro games. The full franchise bundle with 2033 (Redux), Last Light Redux and the latest Exodus can now be purchased for 30 EUR, a 71% reduction.
Recommended system specifications: Quad-Core CPU, 2GB RAM, GeForce GTX 260
Surviving Mars free on Epic Game Store
You can also obtain a free copy of Surviving Mars, a sci-fi building simulator.
Recommended system specifications: Intel 5th Gen Core i5 class CPU, 4GB memory, GeForce GTX 750 Ti or other GPU with 4GB VRAM
Source: Epic Games Store