To be honest, I can't think of an FF outside of possible FFX where its possible to get every item the first time through without a guide. Hell I still find items I never knew about in these titles.

Master Materia, some of the Limit Breaks (like Tifa's and Vincents) and most of the Ultimate weapons in VII don't have any hints.

VIII gives you the formula's for the Ultimate weapons but I don't recall the game ever telling you where to obtain these items. There were also a few GFs that were never hinted to getting in the game. Not to mention how to get Quistis' ultimate Blue Magic

IX... Excalibur 2 need I say more? This game alone is worst than the others cause its guide basically tells you to find out on Square's Playonline network .

X, is probably the only one I can think of that is plausible except for maybe getting the Mirror that grants you access to everything. That mostly requires a bit of dumb luck.

V had the Braveblade/ Chicken Knife and technically a good portion of the Blue magic and several of the strongest weapons in the game are impossible to get without a guide telling you where to obtain them.

VI had the Paladin Shield, a few espers, and blue mage magic that are nearly impossible to obtain without a guide. It also has a few weapons and items that are difficult to obtain by not knowing you need to not open certain chests until later.

IV has the four special summons and countless armor and weapons (Adamant Armor and Spoon Dagger) that are low drops from monsters you could never know about and I-III follow a similar pattern. So frankly, I don't see why people are whining about one damn spear only being obtainable from reading the guide. Its not like you can't just "look it up" at the local Barnes and Noble or on Gamefaqs anyway.