Using top left corner to show unity launcher becomes really handy specially if you are currently opening any maximized window and you want to select anything in the window closer to the left edge.
By default on Ubuntu 11.04 Natty Narwhal the whole left edge when you touch, it shows the launcher, many users prefer the default option, and others including me prefer to use the top left edge for showing unity launcher.
[How To]: show Unity Launcher using top left corner
Run Command Using Alt+F2
also you can run it using the applications and search for “launcher” it will show up under installed applications.