A while back I wrote about setting up DNSMasq for your local development using the .localhost TLD. Unfortunately during my research I came across a lot of people advocating setup using the hypothetical .dev domain under the guise of "DevOps". I hate to say it but this is a bad idea, so consider this post a public service announcement.
Now that I've dumped all over DNS hacking it's only fair that I suggest an alternative. The answer is simple: RFC-2606. You see after the IETF released the list of Generic TLDs they released a list of Reserved TLDs. Reserved meaning that they will never be valid TLDs in a global DNS sense. This is similar to how 192.xxx.xxx.xxx and 10.xxx.xxx.xxx are reserved IP addresses.