My vote goes to Camera+. I've also tried ProCamera which does video. I found I didn't like the effects as much and the UI is definitly not as nice as Camera+. I still us ProCamera for video so my $1.99 didn't go to complete waste.
Its a Korean app, and it has different camera types and lenses.
It also saves all photos automatically to your gallery and in their own file.
so if you accidentally delete in your gallery you can retreve it from the files in pudding
when you search it in the app store its the first one of the two free apps.
its written in korean but the actual app is in english =]
HAVE FUN!!
i was using Camera+ up until recently, i just found King Camera and right now it is amazing, the control over my photos when is editing is insane. and i prefer it's simplest design, reminds me of lightroom a little. And for me the white Balance and Exposure Lock were a complete must.