Can I use an iTunes card to buy Apps in the App Store?

I was wondering if I bought an iTunes card, would I be able to use it in the App store on my iPhone, iPad etc?

Yes you can (:
I bought fruit ninja haha using an iTunes card

It works with both iTunes and the App Store

As a direct excerpt from Apple "iTunes credit can be used to purchase videos, music, ringtones, books, games and apps from the Apple iTunes Store and Apple App Store." Yes, you can purchase apps using your iTunes Credit and it is this that allows so many people (without credit cards) to get access to apps (hence making them so popular).

If you have more than one Apple device, you can get an app on both your iPad and iPhone from a single purchase. Just make sure you are signed into your apple ID on both devices (bottom of the featured page in the App Store app on your iOS device) and you can go to purchased on your other device to get any app purchased with your ID. This works on up to ten devices.

You can even use iCloud to enable automatic downloads over Wi-Fi. This means if you are on a Wi-Fi network and you purchase an app on your iPhone, it will automatically start downloading on your iPad. To enable this, go to the settings app and then choose store and where it says automatic downloads switch the switcher to say "YES" for apps.

Hope this helps