Some of us (like me) still have old macbooks that came with superdrive. Naturally, we have replaced it long time ago with a secondary disk.
Wondering what to do with the now apparent "useless" eject button?
Find below some useful key combinations.

control+eject

Shows a dialog box with following options:
go to sleep
restart
shut down.

command+option+eject

Goes straight to sleep.

control+command+eject

It restarts.

control+option+command+eject

Performs shutdown.

control+shift+eject

Will sleep the display only.

Enjoy ;)