K. Megura wrote the walkthrough (except for the guide to dating Yuffie) on this page from which I got some of the information on the cost of materia, accessories, armor, and weapons and the location of the accessories, armor, and weapons. It also provided some of the information on the enemies list, the descriptions of the enemy skills, the information on level 4 limit breaks, the secrets, and the ultimate weapons section.
Stonerocker for writing the Chocobo Breeding section, the Mini Games section, and for fixing up all other sections.
BradyGames Official Final Fantasy VII Strategy Guide for various, miscellanious info.
Final Fantasy VII Complete Survival Guide by Sandwich Islands Publishing provided the enemy pictures.
Mixing Mike Daniels for his contribution in the "Beating the Weapons" guide.
Case translated the guide to dating Yuffie.
Yasha edited the guide to dating Yuffie.
Below is a list of people who helped K. Megura write his walkthrough:
Andrew Vestal, Edmund Chiu, Erwind, Ian Kelley, Ignacio de Lucas, James Smith, Lim Kheng Chye, Nikki, Tatsushi Nakao, the Final Fantasy VII Database (Index), WhisQ, Nawapong Nakjang, Kenneth Edward Whitten, Paul Nathans, Tom Kinkaid, Andreas Skotner, Phil Rutschman, Jason J. Lukman, KFattyPro2, da Chiken, Eric Eyer, David McGrath, Issac Chong, TKCS Oliphant, Eddie LaRusic, Gary Yang, Zachary Keene, Karl Martin, Eric Capps, Paul M. Arezina, Mike Henry, Jen, Dave Upton, Justin L. Young, Mark Ruidera, Charsten Baermann, Roger Christman, Charles Lee, Jeff Wong, Frosty, Brian Evans, EBWells (Reinhart), Elric, Kythorn, Charles MacDonald, Ignacio de Lucas, Clement, Kameron, Benny Kee, Chuck Cochems, Frank Grayson, Michael Geoff Bridge, Martin Debes (for most all of the new stuff in 1.6, thanks a ton), and Versus Books.