On: Resolving power button issues in Mac OS X Maverick...

[nwh]

In which case alt + ` would be a suitable replacement, as that's the command for window switching.

[shalalala → nwh]

'Command' + '~' switches windows in the current app.

[jesseendahl → shalalala]

For Windows style window switching (across all applications), use Control + F4.

You may also need to hold down the function key if you have your keyboard setup the default way, where things like brightness, volume, etc. are the primary uses of the function keys.

[eyesee → jesseendahl]

It's worth noting that you can remap the key easily from the Keyboard panel in System Preferences. Look under Shortcuts -> Keyboard for "Movie focus to active or next window".