I don’t have an iPhone.  Hell, I don’t even currently have a cellphone of any type… but this game looks pretty cool; It’s called Eliminate: GunRange:

For aiming, it takes advantage of the gyroscope in the iPhone 4, in addition to the new higher resolution screen. Apparently it will not work on the previous iPhones because of that.

Some of the other features:

• 12 high fidelity weapons from the arsenals of today’s elite militaries
• 144 target-shooting challenges set in three different HD firing ranges
• Win medals and compare your results with others on global leaderboards

You can buy it for 99 cents – HERE