Btrfs on my laptop with openSUSE, mainly because it’s default, but also for its snapshot capabilities.
Whatever file system my default Raspberry Pi installation uses (probably Ext4).
NTFS on my main computer With Windows 10, because… well… I don’t really have any other choice, although I know there’s some kind of 3rd party Btrfs driver for Windows as well and you can ever have boot partition formatted as Btrfs, but I think it’s still experimental.