Oh look, it's this thread again.
The Commando lunge is ridiculous, but if you don't kill them while they're running up to get close enough to do it, than it's your fault. They're running straight at you in a game where 2-3 bullets from most guns will drop someone. You deserve to get knifed if they come from right in front of you and you don't put them out of their misery.
Speed knifers are a mild annoyance. You know what's slightly more annoying than people that use speed knifing? People that quick scope with the Intervention. You know what's slightly more annoying than that? Grenade launcher attachment, 2x Thumpers and Scavenger. You know what's more annoying than all three of the above combined? The fifteen millionth complaint thread about how broken Modern Warfare 2 is. If you dislike it that much, fine, just don't play the bloody thing. If you like the game too much to stop playing it over these issues, than that's fine too. Just stop cluttering up the place with all these frigging threads about how much you dislike something in a game that you're going to keep playing anyways.
If you don't like Marathon, Sleight of Hand Pro, Scavenger, One Man Army, Stopping Power, Lightweight, Cold Blooded, Commando, Killstreaks, Akimbo shotguns and G18s, Quick Scoping, Heartbeat Sensors or tactical knives, and you would much prefer to play without these things, than I've got one little bit of advice that may help you out:
YOU'RE PLAYING THE WRONG FUCKING GAME.
The perks, the quick scoping, the ridiculous lunging and killstreaks are all part of the game known as Modern Warfare 2. They're part of the experience, and if you don't like that, than go and play something else.