iPhone Only: Burner generates short-term, disposable phone numbers for voice calls and SMS messages, and then masks your outgoing calls and messages behind that number. If you've ever wanted to call or text someone but didn't necessarily want them to have your phone number—like a potential roomie you met on Craigslist, someone you just sold an old PC to on eBay, or even an annoying ex, this app is for you.
Burner can be used for more than just ducking people or protecting your privacy—for example, if you need to post contact information publicly but don't want to use your real number, or if you're working on a short term project or with someone you'll only be speaking to for a short time, this app is ideal. Generated numbers only last for 20 minutes of voice time, 60 text messages, or 7 days, whichever comes first. Alternatively, you can "burn" the number at any time when you're finished with it. You can even generate multiple numbers and give them labels, so you can keep track of what each one is for.
Once your burner number is generated, it works just like any phone number. You can receive voice calls and texts to it if you choose to, or you can shut it off to incoming communication and use it only for outgoing calls and SMS messages. You can even shunt incoming calls to an anonymous voicemail service, and monitor who's used the number to try and get a hold of you. You have complete control, and at no time is your real number revealed to anyone.
Burner will set you back $1.99 in the iTunes App Store, and uses a credit system to generate burners and keep them alive. The app comes with enough credits for one burner, but if you want to extend your burner or create more, you'll need to plunk down some cash. Credits start at $1.99 and go up from there depending on how many you want, and are all available via in-app purchase.