Cleaner Pro allows you to remove duplicate contacts, merge similar contacts, back up and filter.
It has more than 2 million downloads, and is rated 4.8 stars on the App Store. Normally $2.99.
Others:
Ruler (normally $0.99)
Basic Calc Pro (normally $1.99)
Life Hacks (normally $0.99)
Yoga Poses & Classes (normally $0.99)
Pacific (normally $1.49)
Pic Navi (normally $4.49)
Coloresque (normally $1.49)
What is iPhone user doing here ( pun intended)