This is a compilation of what was a 4 part series article published in Gracie Magazine last year (July - October 2006, GM #'s 112 - 115). Gracie Magazine asked 20 of the best BJJ Black Belts what they thought were the best and most fundamental techniques that can enhance or play a major role in your competition game. To expand upon things, I've added most of the photos from a Google Image Search, and all of the videos from searching You Tube or editing existing clips and reposting them. Take a read, see what you think, and post what your comments and/or additions are to the list.
1. Armbar from the closed guard by Ricardo "Cachorrão" Almeida:
"The armbar from the closed guard is an essential submission hold in Jiu-Jitsu. Your opponent has two arms and one neck, so mathematically the probability of an armbar working versus a choke hold is 2:1. First let’s lay the foundation for a flawless armbar from the closed guard (attacking your partner’s right arm). First, use your left hand to pin your partner’s arm to your chest; your right hand controls your partner’s elbow, pinching it to your own hip. Second, use your left foot on your partner’s hip to pivot your body 45 degrees to the right. Use your right leg to put your partner off balance. Third , the left leg catches your partner’s head. Fourth, pop the hips in.
“Now let’s analyze some shortcomings you might encounter and some tips that will help. The armbar from the guard makes you vulnerable to a pass of the guard; make sure you always adjust your hips after any missed armbar attempt. You are exposed to the slam; develop the habit of hooking the inside of your opponent’s leg with your arm so you don’t get picked up and slammed. Especially in the armbar from the guard, because your opponent is on top, gravity is working against you. Whenever someone tries to stack me, I like to turn belly down to use gravity against my opponent’s arm.”
Here's 2 vid's showing slightly different variations of this technique: