if it's for development purposes then it's wide open. For traffic, nothing beats .com or compares. Sometimes people say geographics is important to which I agree but only to a small extent. Domains are global, all domains are global. You might choose an extension that sounds right, that looks better, that fits the tld. Suppose you choose property for example, very generic but your in the US and you want to advertise your property, maybe you choose property.mn because you live in Minnesota. See, .mn has nothing to do with Minnesota but it fits for this purpose. The door is wide open and there are many reasons to choose any number of tld's if the .com is not available.