I love when fans keep an old game alive. OpenTTD, OpenRA, OpenMoHAA and friends are the obvious ones.

A recent one I came across is OpenZ, a free 3D fan remake of Z, the 1996 Bitmap Brothers RTS with no resources at all, just flags and territory. The Zod Engine did the 2D version years ago, so it's nice to see that odd little game still has people caring about it.

What other projects like this should more people know about?

(OpenZ is on itch, Game Jolt and GitHub, for anyone curious: https://github.com/playopenz/OpenZ)