I've reached the point in the game where I've acquired the submarine and can go exploring the ocean floor. One of the things down there is an airship containing powerful monsters which are the primary way to completely twinking out your party. Each of the monsters that can spawn down there can be killed with the morph skill (does 1/8th attack damage but if it gets the killing blow the monster turns into an item) to obtain stat sources. Drinking these sources is the way to max out your stats. I vaguely recall finding this place the first time I played the game way back in the day and then just sitting around morphing them for days until I was awesome. I get drawn to being awesome so I found myself doing that on the bus yesterday despite it being pretty difficult at this point in time. (Pretty sure last time I did it was later in the game so I was higher level.) Of course, it's one of those things where the more I do it the faster it will become since Yuffie will start hitting harder with her morph and everyone will be higher level so they'll have and easier time surviving the brutal enemies.
I'm pretty sure going to find Yuffie's ultimate weapon would be a good idea since it does a bunch of bonus damage that I think works with morph. (Turns out it's actually in the sunken plane... I guess I missed a room or something and need to head back!) But beyond that, I was wondering if there's anything else really worth morphing. I morphed pretty much everything I could the first time I played (including killing Sephiroth solely with morph damage... He didn't turn into anything which made me really sad. Come on, Square... Turn him into a potion or something!) but that gets tedious. I want to skip that tedium by using the power of the internets...
Unfortunately the internets are failing me here. Surprisingly it would seem no one has bothered to make and analyze a list of morphable items. I did find what purports to be a list of items and I guess I can go through the list to see if any of them are interesting...
Escort Guard - interesting armour item with 6 linked slots and good elemental defenses, morphed from iron man who appears to only exist during the end game sequence
Guard Source - gives you 1 permanent stat increase, can be morphed from 4 monsters (in Mount Corel, Gelnika, Mideel, or the final dungeon)
Guide Book - used to get the underwater materia and morphed in the underwater tunnel which I've already passed and therefore might not be able to get? Apparently it might also spawn in the battle arena?
Luck Source - gives you 1 permanent stat increase, can be morphed from 1 monster (Gelnika)
Magic Source - gives you 1 permanent stat increase, can be morphed from 2 monsters (Temple of the Ancients, Gelnika)
Mind Source - gives you 1 permanent stat increase, can be morphed from 3 monsters (Whirlwind Mazex2, Gelnika)
Power Source - gives you 1 permanent stat increase, can be morphed from 3 monsters (Gongag Reactor, Mount Nibel, Gelnika)
Ribbon - makes you immune to negative status conditions, can be morphed from Master Tonberry in the final dungeon
Speed Source - gives you 1 permanent stat increase, can be morphed from 1 monster (Gelnika)
So really it looks like morphing isn't much use except maybe at the end of the game to finish up some gear, to make killing emerald weapon easier, and to twink out your stats. So I'm not missing much, except that thing I probably already missed. Oh well! Tomorrow on the way to work I'm definitely going back to see how I missed Yuffie's ultimate weapon and then probably morph some dudes. Or maybe I'll just continue the plot because I've already done the morphing a ton of dudes thing in the past? I donno.