Valheim - especially if you fork out for a dedicated server. I was playing with family and friends across the Atlanic, so we'd log on the next day and find new bases and bridges built, etc.

I just wish you could modify and expand the boats!

Airships: Conquer the Skies - a great little 2D airship builder and combat game

Songs of Syx - a fun city builder even if combat is largely unfinished still