All the new Warfront zones have a lot of rare mobs that are lootable once per Warfront cycle. They reset each time your faction gains control of the zone, but it can be really annoying to remember which ones you have killed during a cycle that can be over 10 days long. Some of the rares drop mounts, pets, and toys, so it's well worth killing them each cycle. If not for that vanity items, all the rare mobs has a chance to drop gear and weapons as well, which is perfect for getting those alts geared!
In order to keep track of it, we suggest using an add-on called Warfront Rare Tracker. This add-on gives you a nice UI that allows you to see which rares you have already killed, as well as what items you still need. The vanity items you already own are colored red, and the ones you don't are colored white, so it's easy to find your next target as well.
The Warfront Rare Tracker add-on can cycle between the different Warfronts, and will by default show the one you are currently active in.