Personally, I am paying for ludwig.guru which helps to write better english by searching the given statement in famous newspapers like Washington Post, BBC and etc.

I pay for stellar robotics and cardinal autofill scripts. Most people don’t even know what those are

Dreamhost, which provides the old school control panel style hosting with Wordpress installation

Also Zoho for email.

rsync.net

Maybe they're not little-known here, but their service of a restricted shell to large-storage-capacity machines for backups seems pretty unique.

There are a ton of little known services covered by taxes.

Mubi

not sure how 'little-known', but...

Flickr pro

1and1 domain hosting

Microsoft office 365

"little known"

I doubt anyone's heard of the first 2, the last one might have a few other users.