First off let me state that the game itself is amazing, Infinity Ward did an incredible job creating a 1st person shooter that went above and beyond your typical shooter (Bioshock also springs to mind). Now while playing the multiplayer an idea sprung into mind that would/could improve an already awesome game:
Reset the kill streak so that you get UAV (3 Kills), MOTHERFUCKING DOGS!
(5 Kills), Air-Strike (7 Kills), Helicopter (10 Kills)
Hear me out with the dog idea, imagine playing some of the tighter levels and seeing 5 rabid dogs run towards you...certainly could change team based games (Headquarters etc...)
Not the worst idea right? (NOT actually giving dogs uniforms though).