In MW2 Noob Tubes (underbarrel grenade launchers, RPGs, and Thumpers) were very abused. Me and a bunch of my Xbox LIVE friends are really hoping that they are somehow patched in MW3 multiplayer. A few ideas are :
1: Perks similar to OMA or Scavenger do NOT affect noob tube ammo.
2: Perks similar to Danger Close do not affect noob tubes.
3: More kills to unlock an underbarrel noob tube.
4: Reduced range
Noob Tubes bring a balance in CoD (as proven in BO) but only if they are used correctly.
Comment some of your ideas and maybe noob tubes wont be as abused as they were in previous installments.