Through the press he saw feyswords glittering, glimpsed auburn hair and sparks of pale viridian. Then he was pushed back, until the gate receded from view and thought.
Greg Keyes – The Briar King
As we know from this infographic, planes have levels. For instance, the feywild is approximately level 7 through 20.
Since the PCs and monsters from the feywild have an average level of 13, common feywild weapons can be given an appropriate bonus for a level 13 character or monster. Just as +1 swords are the generic magic weapon of the natural world, +2 feyswords (plus or minus one) are the standard among the feywild eladrin.
Feysword: A +2 mithral blade that glitters in the faintest light. When the eladrin armies march to battle, they do so bearing feyswords.
Advantages: 1) A feysword can be treated as a longsword or rapier, whichever is more advantageous. 2) As a free action, a feysword’s user can cause it to glow like a torch. 3) Feyswords do +5 damage to creatures with the Shadow keyword.
Drawbacks: 1) When a feysword is drawn, it confers a -2 penalty to Stealth checks involving hiding in the shadows. 2) If a feysword is exposed to the sunlight of the natural world for three consecutive days, it becomes Sunrusted.
Sunrusted Feysword: A feysword that spends much time in the natural world is likely to develop a patina of gold flecks along its silver blade: sunrust. It acts like a +1 sword, but has all of the other advantages and drawbacks of a feysword.
Lordly Feysword: Its pommel studded with jewels and its blade an interlocked pattern of mithral ivy leaves, this feysword has an enhancement bonus of +3 (or higher) and is frequently used by fey lords.
Advantages: 1) It is immune to sunrust. 2) It does +10 damage to creatures with the Shadow keyword.
Other planes can have their own common weapons: the typical weapon of the astral plane is a +3 angelsteel greatsword.