RIZING : one of the craziest shooters on WP7 Marketplace finally lands also on your Windows 8 RT tablet with more enemies and a bigger arena! If available, this version can also take advantage of your keyboard and mouse making it even easier to dodge the hellish bullets patterns!
The game is free, with ads showing now and then :)

Windows 8 Store Link
Rizing app for Windows in the Windows Store

Windows Phone Marketplace Link
Rizing | Windows Phone Apps+Games Store (United States)