I'm surprised no one else has suggested of this one. I would like a stab vest perk. I'm not saying that I couldn't be killed with a knife but it would take at least 2 hits and maybe 3 when you get vest pro.
I'm sick of being stabbed by people in games that lag so much that I have to start my stab before I can even see the enemy. Besides it would be funny if someone (one of the guys who just run around stabbing for the whole game) runs up, stabs you and then starts to run off only to get stabbed himself. End of streak you sh1t!!!!