Tac Knife is absolute bullshit. It's beyond overpowered, considering how deadly the knife is normally.
Also, the pistols aren't completely trash... But then again, the balance in that game is kinda fucked anyway. I mean, why go pistols when you can just noob tube with danger close? Or better yet, get any of the other completely overpowered setups...
But even with all that, I still find the game really fun. It's kinda weird, considering usually that sort of unbalance would be more than enough to make me rage an insane amount, but the game is still really damn fun, for some reason.