Four items. The GL attachment. The Barrett with the 'Burster' enhancement (unique item). Basically a variation of some item... I forget the name of it... that is in Ghost or some other game. Dead players explode into chunks which damage nearby enemies. A simple one to add since it doesnt have a silencer option so why not. The Hat Trick '3 weapons' perk. As an example for score streaks, the first award (for the RC) is 30 points and obtained by First Blood (10 points) and two kills (10 each). Many of the 'kill' related bonuses, Backstabber etc, give +5 points as does destroying heli's, sentries and all of those good things. As always, streak score points do not count towards streaks.
The second vid is the background battle audio. The cod4 sound system has two tracks for every map. Front and rear. Most maps, including custom, use variations of one of four front/rear sets: backlot/bog, overgrown, bloc, countdown. Some use none at all. It is now a random choice among 12 new tracks (6 each) for front and rear chosen each time the map is run. Urban, general battlefield, distant artillery, etc. Also a few specialty tracks for forests/nature, bases, winter, quieter environments. The overall volume/loudness are also random each time. Custom maps with their own included ambience or battle tracks (OSG maps are a good example) are excluded. It sounds loud in the second video but player battles and in-game sound fx tends to push it into the background, as in the first video. Much better for immersive audio.