I've found a lot of them you can use a batch file with steamcmd to pull mods. I've heard that's a setting that has to be explicitly enabled by the respective game's devs, but as of yet I haven't run into any where it's disabled (although I haven't tried very many, to be fair). Any game with standalone private server clients that can use mods will have it, and I think most that are available from multiple different storefronts do too.