How about a Kimura lock? Worked for Kimura.
Or if they pull guard, picking them up and slamming them on the back of their head? Remember we aren't on a cushy mat or relatively cushy canvas. Worked for the dude on The Ultimate Fighter 5 (also known as The Most Immature Show Ever 5).
Basically, anything that their sporting/entertianment environment outlaws: strikes to the throat, back of the head, breaking fingers, clawing eyes, testicles, etc. Using weapons..
The only reason those slams worked is because he was unwilling to break his arm. Had he been willing to end that guys MMA career forever, he could of broke his arm before that slam ever happened. Instead he was trying to be nice and get the 'tap'. That is a really bad idea for a street fight. However even then the slams did not really mess him up that much. Breaking fingers, strikes to the throat, clawing the eyes, testicles etc, are all very low precentage. They are hard to do, and have varying effectiveness depending on the person you are using them on. I was once put in the hospital from a groin kick, but before I went down I choked the guy I was fighting out cold. I've broken fingers and it didn't slow me down. I once watched a guy in our club break his toe so it was pointing straight up. He stopped reached down and bent it back the right way then went back to sparing.
While these things can help you, you need solid high percentage techniques to make sure you are in a position to use these low percentage techniques.
Of course obviously weapons would work. And blows to the back of the head are not really defensive moves, that means you are on their back raining shots. Hardly aiki if you ask me.