You don't really see it much in fantasy, do you? Artillery. Cannons, with the big booms and the big balls turning some poor bastards into a red stain and a column of brave soldiers into a slaughter house. Wow, that was a bit morbid, wasn't it? Well, in any case, it's a bit of an anachronism that you don't, especially since cannons existed during the middle ages. The Turks famously used them to batter the walls of Constantinople, ending the Byzantine and by extension, the Roman Empire. Indeed,
according to Wikipedia, Europe started making use of cannons during the late middle ages, with the earliest one being something called a
pot-de-fer, which debuted during the Hundred Years' War.
Granted, I'm still a relative n00b when it comes to fantasy fiction, so I'm probably generalizing. I suppose the reason you don't see them around in fiction is because writers are probably afraid of pushing the tech level to that point because where there are cannons, guns are sure to follow. I don't think that has to be. It would be simple just to BS an excuse for firearms not to exist in a fictional world, especially since the early ones were just godawful - literally just metal tubes mounted on wood.