These are the places I like to hunt the most! What I like about them are the decent drops, good exp, rate of spawn, and how quickly I can hunt one of them. Here they are!
1. Platoon Chronos
These things are great hunting, especially for mages. They give 99 exp, drop pretty good mesos, and spawn pretty rapidly. When I am hunting them in Lost Time <1>, if I hunt the map in a clockwise way then the spots in front of me will almost always have a good spawn of them. When I get to the bottom of the map, there are a dozen+ of them and mobbing them is fun :D. Best thing for mages though is the chance to get an
Esther Shield. They are basically equivalents of Mateons, except Mateons are all the way in Omega Sector and I don't go there often.
2. Master Chronos
These guys are pretty good as well. They give 115 exp and drop some pretty good stuff fairly often when
I was training on them. They spawn frequently, and I can get one in 2-3 hits. I hunt them across from the Platoon Chronos, in Lost Time <2>.
3. Paper Lantern Ghosts
These guys were recently added to GMS. They are in Zipangu, accessible from most towns through Spinel. 93 exp each, reasonable mesos, but the drops aren't really all that great. They do, however, drop Yakisoba (x2)s, which can NPC for 2500 mesos VERY often (I got 20 of them after hunting only about 600 of them). They spawn very often along with Dark Cloud Foxes, and if you take a party there you can rack up some great exp. There arent any resting places in there as well so if your party has a moocher he'll just end up getting killed. They are very easy for me, I get them in about 1 hit (ice) mostly.