This is how I personally feel mw2 could bring back all the people bored with it (including me =) dlc wise.
Firstly I would put a gun pack for sale at $4, including the following weapons:
smgs - mp5 "classic" and the mp7 with stock (acr of smgs.)
snipers - dragunov and the m40a3 bolt action. I personally hated the m40, but 97.34% of other people didn't so....
assualt rifles - g36c and the g3
lmgs - the m60 and the browning .50cal machine gun
shotguns - w1200
machine pistols - skorpion
pistols - m1911, fixed the reload problem of course
launchers - the mlk 6 pack grenade launcher. to balance the 6 round mag it does little relative damage and has a small radius. Can have flash, stun and smoke attachments.
Nextly I would a Foxtrot pack at $6 containing 5 brutal spec ops misions, as well as a specops leaderboard. You would probably need a friend, and they focus heavily on stealth and explosive sequences. Take mile high club, and add juggernauts for example.
Finally I would bring all the cod4 maps back in a bumper pack at $15, with a half price discount for the stimulus and reserguence pack if bought.