/apps/metacity/global_keybindings => run_command_1 => F4
/apps/metacity/keybinding_commands => command_1 => krxvt
gconf-editor でアプリにキーを割り当てられる。

/apps/metacity/global_keybindings => run_command_1 => F4
/apps/metacity/keybinding_commands => command_1 => krxvt