AAQR: HydroTilt Live Wallpaper (free, $0.70)

Hydrotilt is basically a "fluid sim" where it pretends your phone has some sort of liquid behind it. In the free version it's just water.

In the paid version you get beer or champagne.

Tilt the phone and watch the liquid level react to the "sloshing around". It is... somewhat amusing.

HydroTilt Live Wallpaper Free
https://market.android.com/details?id=com.codeglue.HydroWallpaperFree&feature=more_from_developer

HydroTilt Live Wallpaper, $0.70 (approx)
https://market.android.com/details?id=com.codeglue.HydroWallpaper&feature=more_from_developer