Vern5 said:
It's always magical/sacred swords.
Seriously, in almost every fantasy media there is a magical sword or even multiple magical swords that seemingly decide the fate of the entire kingdom/empire/cosmos. I can even take JRPGs into account with this trope.
Examples: Soul Edge/Calibur, Excalibur, The Vorpal Sword, The Buster Sword, The Master Sword, Soul Reaver, Froustmourne, Umbra, Narsil, Glamdring, Sting, etc.
The list goes on and on.
yeah, it's a trope, several in fact:
http://tvtropes.org/pmwiki/pmwiki.php/Main/InfinityPlusOneSword
http://tvtropes.org/pmwiki/pmwiki.php/Main/SwordOfTruth
http://tvtropes.org/pmwiki/pmwiki.php/Main/CoolSword
http://tvtropes.org/pmwiki/pmwiki.php/Main/ElegantWeaponForAMoreCivilizedAge
http://tvtropes.org/pmwiki/pmwiki.php/Main/EveryJapaneseSwordIsAKatana
http://tvtropes.org/pmwiki/pmwiki.php/Main/InfinityMinusOneSword
http://tvtropes.org/pmwiki/pmwiki.php/Main/PenultimateWeapon
http://tvtropes.org/pmwiki/pmwiki.php/Main/KatanasAreJustBetter
http://tvtropes.org/pmwiki/pmwiki.php/UsefulNotes/Swords
http://tvtropes.org/pmwiki/pmwiki.php/Main/SwordOfPlotAdvancement
http://tvtropes.org/pmwiki/pmwiki.php/Main/UltimateBlacksmith
http://tvtropes.org/pmwiki/pmwiki.php/Main/AbsurdlySharpBlade
http://tvtropes.org/pmwiki/pmwiki.php/Main/LikeCannotCutLike