The motto with Linux is customization right? So lets customize the shortcuts in Gnome to make them do what we want them to do.
If you are looking for a list of default Gnome shortcuts check out, All the Best Linux Cheat Sheets.
First open up the gconf-editor
Then in gconf go to apps > metacity > keybinding_commands
You will see commands ranging from 1-12. These are your custom command aliases. Select one that is not in use. Lets say command_1
Then type in the command that you want ran.
No on the left side of gconf go to global_keybindings.
Find the corresponding run_command_ and double click.
In the value you will type in your shortcut for example, <Control><Alt>S
Now for this example Ctrl+Alt+s will open up the gnome-system-monitor.
Just remember to try out the shortcut before you override it. You probably don’t want to assign a shortcut to something that is already used for something more important. There are also some preset shortcuts you can set in System > Preferences > Keyboard Shortcuts.