Very nice option to switch windows is Contexts app. It allows you to switch applications using Alt+Number. It provides a sidebar with all running apps and ability to replace Cmd+Tab including smart search through currently opened windows.

However I often prefer to use a keyboard shortcut that doesn’t change – for example Alt+x for XCode and Alt+c for Google Chrome. BetterTouchTool is very handy for this. Just create a keyboard shorcut, use Execute Terminal Command action and put configure it with similar command: