We can open the "Run Application" dialog of GNOME pressing the F2 key while holding the Alt key.
In this dialog we can type the name of an application and then press the Enter or Return key (or click on the Run button) so the desired application opens. For example, if we type totem and press Enter the Totem movie player opens.
We can also type the address of a folder so Nautilus opens in that place. For example if we enter /etc Nautilus opens in this directory.
This dialog helps us entering the data. For example if we type ged automatically gedit is offered.
This dialog can run any of the many applications inside /usr/bin .
Here is a list of the ones I use more often:
gedit : gedit (text editor)
gnome-control-center : GNOME Control Center (control panel)
gnome-terminal : GNOME Terminal (terminal emulator)
xset dpms force off : turns the screen off (useful for laptops)
eog : Eye of GNOME (image viewer) (not necessary because it opens when we click on an image showing that image -if it's the default application for the image format-)
file-roller : File Roller (archive manager) (not necessary because it opens when we click on a compressed file we want to decompress; and there is a Compress... entry on the menu when we right click after having selected one or more files we want to compress)
gcalctool : gcalctool (calculator)
gconf-editor : Configuration Editor (user preferences and system configuration data editor for the GNOME Desktop and many applications)
gnome-search-tool : Search for Files (file searcher)
gnome-session-save --logout-dialog : "Log Out of the Session" dialog (to finish or close the session; or to switch or change the user)
gnome-session-save --shutdown-dialog : "Shut Down the Computer" dialog (to turn the computer off, reboot it, suspend it or hibernate it)
totem : Totem (movie player; also plays audios) (not necessary because it opens when we click on a film or song)
xcalc : xcalc (calculator)
xterm : xterm (terminal emulator) (gnome-terminal has an useful scrollbar)