Guncraft Blocked and Loaded

So what the other solution doesn't mention is that rank rewards tend to be random. This unlocked around the last Warrant Officer rank for me however it may be earlier or later.

To do this simply:

Equip from the Customisation menu under customize class. Select one of the custom classes. At the bottom you can select killstreak rewards, you can only equip three of different numbers (Seen to the left, showing how many kills needed to use the kill-streak reward). Anyway it will be near the bottom of the screen, so simply select and save it.

Now use these Xbox-Live settings once you and your guest account are in a Deathmatch lobby:

Map: Flatworld
Time unchecked
Kills: Whatever number you want, minimum of 3.
Unlimited resources

The rest of the settings as whatever you want.

Apply the settings.

Now once you load up and press to enter the game, the spawns are linear.

Just go to either side of them and hold down + . Make sure your other account is firing to get rid of the spawn shield. You will mow the account down until the reward shows up to the left of the screen.

Looks somewhat like this:
http://tinyurl.com/ord9ba3

Now the reward can be turned on by selecting the D-pad direction for the kill-streak reward. A box will appear in front of you place it on the square where your account spawn and press to unleash the bunker buster bomb.

Don't steer the bomb and it will land on the accounts head every time. If it somehow misses jump off the edge to reset the kill-streak.

Rinse and repeat.

The Bunker Buster is one of the first kill streaks you unlock. From the main menu, go to "Create a Class". From there you can select your kill streaks at the bottom. Simply select the Bunker Buster, save the class, get into a game, get a 3 killstreak to unlock it, and directly hit someone with it. Very easily boosted.