I know of people who registers for new domains and then sell them. You can get some great sounding names which people may want to buy like american.ninja or marketing.ninja or wealthyaffiliate.ninja otherwise I would stick to .com . Hmmmm...wealthyaffiliate.ninja actually sounds nice....:)

Hi,
I'd say the pros include greater availability of the domain name you're looking for since so few will have been taken already. If your niche website is one that has you building a reputation for yourself as an expert, not just knowing your stuff but doing it well, then you might want to be known as a ninja in that niche.
The main con, as Michelle pointed out, it is a Top Level Domain (TLD) that is new and therefore not well known. I suspect that over time all these new domains will be better known, more widely accepted, and just one more detail to remember when you remember a URL. A lot like phone number area codes are now. When I was growing up you didn't need to use it unless you were dialing long distance, but then, over as more phone numbers were created it became necessary.
How much does it cost? $5/year? It might jump up to $15/year after it becomes established? You could always buy it and park it. You could use it later, maybe as a related product/service to what you are doing now.

Cheers,
Mark

Hi. I would not recommend getting any of these types of domains that are usually not heard of. Kyle tells us that we should go for a .com, then a .org, and finally a .net when getting a domain. They rank best and you are better off going with an extension that people know and use.