Play Brave[1] is a game from the Born This Way Foundation, which uses Persona.
Mineshafter[2] is a free alternative to using the main Minecraft online services.
The Times[3] (UK) Crossword puzzle uses Persona to make switching between Desktop and Mobile easy.
[1] http://www.playbrave.org/gallery/ [2] http://mineshafter.info [3] http://crossword.thetimes.co.uk/