I had some custom scripts that I had custom launchers for on my desktop on 10.04. I would like to recreate that again after migration to 12.04, but unity seems quite foreign to me.
I have answered a similar question here.
Briefly, copy the nearest script from /usr/share/applications/ to ~/.local/share/applications and then edit the xyz.desktop file. The line that starts Exec= is the line you need to edit, to put your own command in, along with whatever command line options you want. You will probably also want to edit the Name= line to describe your own script.
Once you've done that you'll need to restart your computer or log out/log in, then you can hit the Super key, start typing part of the name you set and your launcher should appear. Select it and hit Enter and it will run your command.
