Focus on a application Can I create any shortcut to focus on an application? 

For instance ⌘ CMD+1 and Safari is active and on top of other windows, ⌘ CMD+2 Pages and so on.

I remember a long, long time ago, that was possible with F1, F2...
You can do this with many apps available. I personally prefer Better Touch Tool, because You can do much more than just assign keyboard shortcuts. There's window snapping and most of all - custom mouse/trackpad gestures. Here's example:



With this I can press ⌃ CTRL+⇧ SHIFT+1 to focus on Safari.app.