Hell, “Castle Walls” is a standout…everything. It follows the same template that B.o.B.’s “Airplanes” and Eminem’s “Love The Way You Lie” previously used, but “Castle Walls” ends up being better than those two songs for a few reasons. For one thing, Christina Aguilera is a better singer than Rhianna and Hayley Williams, and plays her role better than both singers. For another thing, “Airplanes” and “Lie” sacrificed personal sentiment for mass appeal (and managed to great songs in spite of that). T.I. remains honest about himself and lets Aguilera handle the whole “mass appeal” business. It is one of the best songs I’ve heard all year, and it is a hell of an album closer. If you listen to only one song from this album, make it this one.