How to choose a application without using the mouse in Lion Mission Control? While using Mission Control and pressing Control ⌃+↑, I get the tiled view of all the applications in that particular desktop. Is there a keyboard shortcut to choose an application in this view?
No.  I haven't found any, but that's not surprising.  Mission Control was provided for mouse / touch interaction.  Have you tried using Command ⌘+Tab for app switching and Command ⌘+`for window switching? 

They are much more efficient if you're interested in keeping your hands on the keys.