The script shows a dialog and you can simply enter the Name of the application which has to be launched:
tell me
activate
set s to display dialog "Which appliation do you want to start?" default answer "Safari"
do shell script "open -a \"" & text returned of s & "\""
end tell
Copy and paste into the AppleScript Script Editor, save it as an application, and then use DragThing (or similar) to assign it a hotkey.

