A Japanese ancient weapon, Ninja's Shuriken.
You may sometimes not be able to find the cursor on the dark themes.

On GNOME,
1. open System> Settings> Appearances, select 'Themes' tab.
2. drop archived file onto the window.

On Xfce,
1. Untar the file into ~/.icons.
2. go to Settings Manager> Mouse, on Theme tab, select this cursor theme.
3. On some distibutions, you have to re-login.