This works unbelievably well in Blood
Gulch. The best part about it is that you'll only need one (or two to be safe)
people to do it. All you need to do is get a shotgun. Next hide in one of the
cracks in the base or in the area closer to the door. When someone grabs the
flag, they have no weapon to fight with , so all you need to do is buckshot them
once or twice and they are gone.
To make sure they don't come in on the side that you are on, just watch your
motion tracker and go to the side of the base opposite the side they are
entering.
There are possible ways to get around this, but hers how to make it work again:
1. They throw grenades first - Don't wait in the area by the flag, wait closer
to the door for easy escape.
2. 2 people come in - just throw a grenade by the side entrance, and wait for
the other shmoe to grab the flag.
3. They drive a car close - throw a grenade !
This can also be done with a rocket launcher , but is not recommended since it
has very limited ammo. This has worked for a few months for me ,but our
competition starts to figure it out. definitely worth a try.