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ProCapture is free and Plus is a deal at $3.99. It's got the fastest shutter on the market and functions very well in all conditions. There's no post-picture editing.
NightCamera is free and + is $2.99. It nails taking Android smartphone photos in low light, and has plenty of options to get the just-right nighttime shot. The shutter is screen tap only and sometimes crashes between functions.
Instagram, just acquired by Facebook, makes crappy photos look artsy and cool. Plus, the shutter is quick. The camera is limited and is only available in a gated community.