In addition to all the above:
Scroll lock is still used by excel (2002 at least). When pressed, and when using the arrow keys, the window will scroll but the selected cell will remain selected. Useful to snap back to where you were. Similar to mouse wheel in word, and then snap back with an arrow press but in excel, it's on the y and x axis.
Pause/Break is actually more powerful than Ctrl C when in an IDE such as (DOS) Borland C. Ctrl C would attempt to kill the running process. Ctrl Break would kill the IDE and return you to DOS (bye bye any unsaved changes but better than rebooting).
Pause itself was useful when 486 dx2s + (pre ME) came out and DOS/Windows boot screen would be loaded before the monitor could display all the himem, emm386, tsr loads etc... I still use as the other day my PC would reboot just before it reached the XP login, but just *after* displaying a 80x32 style DOS screen telling me what the matter was. Took a few attempts at pausing at the right time
Finally, Print Scrn is great, especially in a MMWIE (Massive MultiWorker Indoor Environment) where screen-shots are required. As Eric mentioned, Ctrl Prnt Scrn will capure the desktop, but ALt Prnt Scrn will only capture the active window.