I love play 'An Ultimate Hunt' on my HTC One X when I have free time and it also release a lot of tension. Here's the rules.

Shoot as many birds as you can in the limited time.
You get fines if you shoot the wrong birds. Must not have many fines to not lose the level.
You must be very careful because the birds fight back with help from some of their friends.
For hunting you earn virtual money.

This in one of my definite favorite game. It’s fun, interesting and easy to use.

Here's some screenshots I've found for you to understand..




You also can download and enjoy shooting birds.