I depends. But as others have said I would try to get creative with the name to find a .com for it. PG recently wrote a post on changing your name but I don't agree with it 100%. http://www.paulgraham.com/name.html

However if your product is a mainly accessible via a mobile app then I would use the .co or other clean TLDs. For example, Vine is still using .co and it's a massive success.