No gathering of equipment would be complete without magical items. Until I work up a list of some of my own (including updated versions of some of my players' favorite 2nd Edition items), here are some armor qualities:

Most magical equipment meant to be worn resizes itself to fit any wearer, whether Small or Large, and sometimes e'en more. Rings, boots, gloves, cloaks, helmets an' belts all fall into this category.

However, these items're either single pieces or come in a pair. Armor, on th' other hand, 'specially heavy armor, is actually made up of many pieces, includin' paddin' and straps. This makes magic armor made fer a kobold useless to an elf, while magic armor from a dwarf don't do a gnoll no good. Furthermore, if a basher's a shapeshifter, things get even stickier.

Resizing: This armor magically grows or shrinks to fit a wearer from size Tiny to Large. The change in size occurs immediately as the armor is donned. The wearer must have the same general bodily structure as the being for whom the armor was originally made (same number of limbs with similar placement, etc.).
Faint transmutation; CL 5; Prerequisites: Craft Magical Arms and Armor, shrink item; Market Price: +1 bonus.

Reshaping: This armor magically grows or shrinks to fit a wearer from size Diminutive to Huge. In addition, it will change its shape to most effectively protect the new wearer, regardless of the wearer's shape or build. The change in size (and shape) occurs immediately as the armor is donned. When the armor is removed, it reverts to the shape it had when originally forged.
Moderate transmutation; CL 9; Prerequisites: Craft Magical Arms and Armor, polymorph, shrink item; Market Price: +2 bonus.

Retaliator: This quality may be put on armor and shields. When the wielder is damaged in combat, a retaliator item bursts forth with a spray of energy, causing 1d6 points of damage to the attacker. There is no saving throw against this damage, though energy immunity, damage resistance and other protections still apply.
An energy type is chosen at creation, and can be acid, cold, electrical, fire, force, holy, profane or sonic. Other types of energy may be applicable if other energy types are available.
Moderate conjuration; CL 9; Craft Magic Arms & Armor, fire shield; Price +2 bonus.

Retaliator, greater: This quality may be put on armor and shields. When the wielder is damaged in combat, a retaliator item bursts forth with a spray of energy, causing 2d6 points of damage to the attacker. There is no saving throw against this damage, though energy immunity, damage resistance and other protections still apply.
An energy type is chosen at creation, and can be acid, cold, electrical, fire, force, holy, profane or sonic. Other types of energy may be applicable if other energy types are available.
Strong conjuration; CL 11; Craft Magic Arms & Armor, fire shield; Price +3 bonus.

Retaliator, lesser: This quality may be put on armor and shields. When the wielder is damaged in combat, a lesser retaliator item bursts forth with a spray of energy, causing damage to the attacker equal to the actual “plus” of the lesser retaliator armor or weapon. There is no saving throw against this damage, though energy immunity, damage resistance and other protections still apply.
An energy type is chosen at creation, and can be acid, cold, electrical, fire, force, holy, profane or sonic. Other types of energy may be applicable if other energy types are available.
Faint conjuration; CL 7; Craft Magic Arms & Armor, fire shield; Price +1 bonus.

Equipment Pt. 1
Aerial Equipment Pt. 1
Aerial Equipment Pt. 2