I sure hope the list of bugs I know isn't too greatly duplicates of others.
player hp and mp can exceed 9999 and 999 respectively, both can reach up to 65535, exceeding resets values. (already know this is known though)
enemy hp and mp can similarly overflow to above, if enemy hp or mp reach close enough to 65535 and cure is casted, it may overflow their hp, thus the next hit would kill.
attack stat can overflow if it hits above 255, it could be achieved if a weapon had 205 or greater attack and user's strength is 99 while not equipping a shield, it could more easily happen in battle if berserk is used while at high enough level.
its possible to overflow weapon/spell growth if you target cancel or do the same action 256 consecutive times in a single battle (though have not confirmed it can occur with magics), the end result is leveling up every battle afterward automatically.
if Starfall is put into enemy AI outside of final battle, it will not be used at all, if used forcibly via player using item magic, the spell animation will freeze the game.
the wall bug is the result of wall forcing the animation of whatever spell directed at the target to play in full, and since instant death spell animations remove the enemy graphic from field, it works as the vanish/doom of ff2. If it was possible to instead have wall force a specific animation like how absorb forces cure animation, that could fix?
having any status effect that does not wear off at end of battle, at end of battle, prevents any growth in any used skill or spell, rather than just for petrify, toad, and KO.
The graphic of the final battle Emperor is missing a tile in battle, Tile EA. However, it is a blank tile, a quick hex edit of the name table location (which fortunately is not compressed), will fix it.
any status effect afflicted by weapon will hit whether your equipment has resist to spells that inflict that ailment or not, the only prevention of physical attack afflicted debuffs is high magic defense, gained either naturally or via shell spell being stacked in battle. The bugfix of later versions of ff1 treated their counterpart of this instance as a bug while ignoring the ff2 version in later ports, enabling ancient sword to inflict curse with ease, or if killer bow was accessible, one hit kill any enemy in the game.
another issue with Wall is it blocks exclusively black magic category spells, even beneficial spells like berserk or haste get blocked, future ff2 ports allow buffing black magic to be unaffected by wall, but also disallow wall from blocking white magics (presumably because it would be far too powerful a spell when it blocks even ultima).
Well, that's all I can think of right now, if i can recall any more, i may post.