Sure do..I know the feeling well
If you have a lot of patience the Adamantoise (those are the ones with the spikes around their feet are the daddy ones) can be killed by Vanille's Death spell. The chances of it working are tiny, but if you call her summon they fall over so you have more goes at trying to kill them with it. Ignore the adamanchelid's tho.
When they die they give 40,000 cp and have a small chance to drop the material that morphs a weapon into an ultimate weapon (Trapezohadron). Also the Ingots that they drop sell well so your patience does pay off