Warriors/drg/drk/ etc with provoke. Paladins are the best tanks, Ninjas can, in some rare, expensive situations be almost as good, paladins are THE tanks.
Now, Paladins do not pull, they rest in between fights to regain MP. When pulling, DO NOT USE PROVOKE. If you do, when you get back to the camp, the Paladin cannot simply voke it off you and begin tanking immediately. Since the puller likely does more damage the mob will stay in him. One way a Paladin keeps hate is by curing himself, If I'm not taking damage I cant do that.
Bottom line, if the Paladin in the party is designated primary tank, dont pull with provoke, go spend your precious 500 gil and buy a boomerang for god's sake. Its oh so simple.