For me it was Gentoo. I am not sure what it is but for my work it just works better. Tests shows it runs faster for my work and comes with all the tools I need to compile things. I really like the package naming scheme and use flags. I also like the custom-ability of it as well. Tried arch and others but hated it. Also I think the documentation on Gentoo is insanely good.
I have enjoyed caves of qud. Feels like every run is brand new.