Weapons in video games are one of the most deceptively hard things to figure out, both as a player and as the developer who has to create those weapons to begin with.
Generally speaking, a video game weapon needs to be at once useful, versatile, and feel really good to use. You should not only have a weapon that's fun to use, but whose usefulness extends beyond what it seems to be on the surface.
And then you have the other guys.
Some video game weapons, whether due to shoddy design, lack of understanding of the mechanics of the very game it's in, or even the developers intentionally trolling their audience, are just flat out bad.
A bad video game weapon can take many forms, but the main rule for getting on this list is that there must be a standard of good within the game itself. Otherwise this list would be filled with every weapon from Daikatana.
Otherwise, if you can use it to cause harm to another character in game, then all bets are off. These are by far the worst video game weapons ever made.