Or other things you notice?

A couple things I have noticed/try out:

One man Army to Hardline Combo: I start off using a class with OMA and Stopping power, when I get 2 kills before a kill streak, I use OMA to switch to a class with Hardline. The next kill gets me my kill streak.

Last Stand w/ Akimbo handguns. Once you get your handgun kills up to Akimbo, I put it as my secondary weapon. When i go into last stand or Final Stand, you will put out your akimbo pistols it is pretty much an instant kill on the person who killed you.

Emergency airdrops: The Emergency Airdrop plane comes in the direction that you throw the package grenade. So if you are in a corner of a map, do not face a wall and throw the grenade or else the plane will have to travel across the entire map to drop the packages.

Full Metal Jacket. I use this weapon attachment a lot. One of the problems I used to encounter was people would duck down underneath low walls when I hit them. With FMJ, i shoot right through that wall and get them. Really effective on Skidrow when they come around that long hallway and try to duck down behind that low wall.

Harriers vs Helicopters. I still see people calling Helicopters (attack, pave lows and chopper gunners) when there are enemy harriers out. Enemy Harriers will automatically shoot down your helicopters, so watch out.