Camera+ $2.99, camera.plus

This is a killer app both for taking better photos and tweaking them so they look as good as possible. Manual focus, white balance, exposure, and shutter speed controls are all easily available when shooting. You can shoot raw photos, and there’s a big range of options to customize on-screen indicators. Its editing tools include many of the kind of adjustments and filters you’d expect, and also the fantastically clever Clarity filter, which makes even the dullest photos look vibrant and exciting. No snapper should be without this.