Can be anything from any source, movies, books, comics, video games, manga, anime etc.
Pic related is mine, the dragonslayer from berserk. I like it because it’s simple. It’s just a big fucking sword, no fancy bells and whistles like enchantments or spells.
Second runner-up is sting from lord of the rings, I like that it glows blue when orcs are around and it can be used in the dark as a light source.
Guild Wars 1 had a lot of unique and weird weapons but the Fiery Dragon Sword is one of those rule of cool weapons even though it makes no sense practically.
Yeah nonsensical fantasy sword still looks cool