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.
Honorable mention: Detritus's "Piecemaker"
*edit: https://wiki.lspace.org/Piecemaker
There is a tradition, right across the Multiverse, of macho law-enforcers toting ridiculously heavy sidearms, which surely represent overkill for normal policing duties. Dirty Harry had his .44 Magnum; Detritus carries a siege weapon with a two thousand pound draw.
As Detritus considers this a waste of energy if all the energy devoted to drawing back and cocking the string is only expended on a single arrow (which from a human point of view is a six-foot lance), he has adapted it still further, so that it shoots a bundle of twenty or so arrows bound together around a central core. Due to the violent force acting on them, the arrows tend to disintegrate into a cloud of supersonic (a significant fraction of local lightspeed) shrapnel which bursts into flame from air friction. The resulting fireball scythes everything in its path totally clean. Hence the name. It not only opens front doors, but frequently creates a back door as well.