Balancing, especially in multiplayer-oriented games, is a tricky thing to get right. Each and every weapon must be taken into account to ensure there isn't one that stands out from the pack with too many strengths.
It's a rock, paper, scissors scenario with weapons speed, power, and other dynamics needing careful attention to ensure no matter what the scenario may be each player has a chance at coming out the victor.
In the old days, when it was just you and your friend sitting side-by-side without a care in the world with a focus on pure fun, balancing wasn't so much of an issue. However, once multi-player advanced into a more competitive spirit if there was a strategy to be exploited, you can be sure it was taken to ensure you came out on top.
These ten weapons became so cripplingly over-powered they ended up dominating their respective games to the point players would be forgiven for giving up and never playing them again without nerfs.
Be it they were given an unfair advantage, crushing damage output, or there was simply no defence against them, they all plagued gamers nightmares due to the frustration generated from their use.