[Aerich]

I can't think of any specific "must-have" awesome item off the top of my head that is alignment-restricted, aside from the paladin's sword. Certainly nothing that can't be substituted for. It's usually weapons or armor.

So many of the items are random, and a well-balanced party will have plenty of good loot to choose from - towards the end of the game you will have too much. I think people bemoan their alignments because they missed the opportunity to use a "cool" item, not because it offers that much advantage in the game over another item.

Just on general principles, you may wish to make either the fighter or the fighter/thief a neutral or evil character. These are the only two where I think you have some latitude to choose (Paladin is set, F/D is set, Ranger is partially set, and good C/Ms have the advantage, as shown below). Maybe the F/T; there's some poisonous weapons available, and it would seem strange RP-wise to have good characters using poison weapons all the time.

I would definitely make the C/M good. Evil clerics lack the greater healing spells (Cure Critical Wounds and Heal, possibly also Raise Dead and Resurrection), and I believe neutral clerics cannot access the "Shield of Lathander" spells.

Your ranger has to be good (class requirement) and I don't think lawful, neutral, and chaotic are very important, except for RP.