Exploit or not.. you guys want a grief fest? Get the Carepackage in your hand, using Marathon/Lightweight/Commando it makes pretty much everyone in-game cry out loud. I'm seriously thinking about recoding it, but Fraps records the audio out of sync, and there's no way to demorec. D:
I went 47-6 in one game only using melee kills (and Harrier), and 3:1/2:1 in pretty much every other games I've played, only running around, "knifing" people. Granted, they weren't all that good, but the thing really provides an extra speed boost. And I do believe that it works like a tac knife attachment, too. So you don't need tac's anymore.
I also recall getting 10 melee kills in less than 14 seconds and around. It was hilarious. There's just no way I'm turning around until they fix it. If they ever do. Also, nukes are completely out of the question, they just ruin the fun when you drop it on them.
In case anyone is interested, this is what I use.
[screenshot]http://img39.imageshack.us/img39/6799/mw2setup.jpg[/screenshot]
SMG/Snipers provide faster movement to your class. So you'll want that too. Don't use a assault rifle as it doesn't benefit from full speed.
I'm thinking about replacing the RPG for a JAV. The thing is more useful with DangerClose.