WAAARRK!! Sh1+!!! Chocobo WEAPON!! lol
I've done a lot of research concerning this topic and by a lot, I mean, very little. I've turned up some promising tips toward encountering the legendary WEAPON and by promising, I mean, asinine tautologically blatant lies.
WARNING! Chocobo Weapon does not exist in Final Fantasy VII... but if it did, it would be difficult to find and the most frustrating enemy to fight, given it's tendancy to run away when actually threatened and its insane power that puts even Emerald and Ruby to shame.
*(Not that I'm saying it's real), but if it were, you'd need to accomplish the following to reach it:
1: Obtain all of Aerith's weapons and don't sell any.
2: Breed two Gold Chocobo's and rank them to S.
3: Defeat Emerald and Ruby and DON'T give the items to the old man in Kalm.
4: Use the Silver Chocobo to dig under the surface of the Zolom Marsh. The chocobo senses something familiar and dangerous.
5: Tell the weapon seller near Gongaga about what you've found and he'll tell you about a mythical weapon that can be of great help to you. You'll have to sell him all of Aerith's weapons to trade for the Chocobo Eater. Not that it really exists, but if it did, obtaining the Chocobo Eater is the only way to convince the Silver Chocobo to proceed further down into the marsh to dig up Chocobo Weapon.
6: Your first encounter with Chocobo Weapon will always result in IT running away.
7: Give the items you obtained from Emerald and Ruby to the Chocobo Sage and he'll use them to synthesize a special type of greens. He warns you that they're not enough to keep the Chocobo Weapon around indefinitely.
Defeating the non-existent Chocobo Weapon:
1: Max your damn stats.
2: Buy one of every type of green.
3: Equip Cloud with the Chocobo Eater.
During the battle start with your greens of least value. You'll need to feed CW every time it looks distressed. Every time you feed it, it's HP will be completely healed, but if you haven't been inflicting damage, the greens will have no effect and CW may run away. It may also run away if it seems you've stopping paying attention to it (i.e. attacking). Work your way up through the greens to the Sylkis and when the CW seems to be distressed again, use the special greens you obtained from the Chocobo Sage. This will make CW drousy and confused. It will berserk and kill everyone in your party, so make sure to cast Auto-Life using the Can't Kill Me materia you obtain by trading the Compass with the Weapon Seller... not that it exists.
The mythical Chocobo Weapon's defeat results in the Chocobo Eater transforming into the Chocobo Weapon for use by any member of your party. The Chocobo Weapon (not real) is a gunblade that hovers alongside the wielder and acts as an attack dog. The Chocobo Weapon is so powerful, it can defeat Jenova Synthesis, Bizzaro Sephiroth, and/or Safer Sephiroth in a single attack. It comes equipped with a summon materia to summon Chocobo WEAPON into battle. Chocobo WEAPON is so powerful that using it at any time in the game results in a game over. This is accompanied with a new FMV wherein Jenova, Sephiroth, Genesis, and the Tsviets all melt or explode.
Not that it exists, but if it did, the Silver Chocobo would have the ability to dive underwater with the help of Sylkis Greens used on the World Map. It's not a submarine, so you can't use it to reach the Gelnika or anything, but it can sniff out treasure just under the surface of the water. Not that there is any, but if there were, there would be very few spots scattered across the large ocean.
Silver Chocobo, which doesn't exist...
1: Obtain 500 Carob Nuts. Obviously, since your max carry is 99, you'll have to sell some of them at the Chocobo Ranch or at the Chocobo Sage.
2: Obtaining 500 Carob Nuts means fighting Vlakorados 500 times. After the last battle, roam around the area outside of Bone Village and there is a 2-3% chance you'll encounter the mythical Mini-Vlakorados* not that I'm saying it exists which will drop a Vlakorados Liver upon its defeat.
3: Give Chocobo Sage the Vlakorados Liver and he'll ask you to obtain a Zeio Nut.
4: Giving Chocobo Sage a Zeio Nut prompts him to use the Liver to alterchange the Nut into a Pegasus Nut.
5: With Vincent and Yuffie in your party, use the Pegasus Nut to mate your S Rank Gold Chocobos to birth a Silver Chocobo. Cissnei will appear to congratulate you and promptly disappears.
