Other Uses
Because the key is otherwise rarely used, programs that tie into other software often use it to prevent issues arising from both programs using the same key. An example could be two game overlays using same shortcut, which will crash the game.
The indicator light is also sometimes used in certain applications, as well as Keyboard Layout Indicator in some Linux distributions (like Ubuntu) because doing so is less likely to cause problems than manipulating other keys/lights.
In Microsoft Windows 2000 and later, a registry setting can be changed to enable a debugging feature that allows the user to manually crash the system, generating a memory dump for analysis. Once set, the user can hold the Ctrl key and tap the Scroll Lock key twice to trigger a BSOD.
Belkin has released a 2-port KVM switch that uses the Scroll Lock key on the keyboard connected to the switch for selecting between computers. The switching is accomplished by pressing the Scroll Lock key twice, and then selecting either the "up" arrow key to select the first computer, or the "down" arrow key to select the second computer connected to the switch.
Read more about this topic: Scroll Lock