I have a few for failed armbars, though if they have the wrist clasp position you can always keep fighting them and work to sink in your legs with the armbar. That's not a lost cause.
The bicept slicer has already been mentioned, so I'll go down the list and leave that one out.
Omoplata This is really the classic technique, used by everyone from the Nogueiras to the Gracies. You have to pull the wrist free to lock in the technique, but it works just fine once you roll over and grab the waist to keep your opponent from rolling out of it. I won't give a technique for this one, because it's a pretty common move. If someone wants it, just ask.
Omo-mura This is a variation I learned from watching Claudio Franca, a local fourth degree BJJ blackbelt. I don't like him much, but the move works. It's basically an omoplata set up where you keep your weight in front of your opponent instead of rolling behind them for omoplata leverage, and you apply a kimura armlock.
Reverse Ten-Finger Guillotine This is my really complicated move for the guard position. You start by transitioning either back to guard or to triangle, and while you are transitioning wrap your hands around the head for a guillotine position. The traditional "David Brennan style" ten finger guillotine actually uses the thumbs up in a flat palm (almost old school Kempo bow) to apply the choke, what I do for this one is apply it using my hand blade (the pinky side of the hand) or the knuckles. While you really need to sink this in to make it work, I've found that it's very effective and applies very good neck compression.
Toe-hold Swing your legs over to the reverse triangle body lock position (a la Josh Barnett) and lay on the toe-hold. The hardest part is getting your leg to clear your opponents opposite side arm to get the body triangle. Personally, I suggest using the knee to cut straight down across the body instead of trying to clear the arm.
Mounted Gogoplata This is actually one of my favorite techniques. Roll your hips over like you are transitioning to an omo, but don't let your opponent's head escape. Then sit up (this requires some hip flexibility) and sink in the gogo. If your opponent sits up during the technique, trying to fight their way out, grab their head and sink in the gogo in the traditional, back-on-the-floor position.
Power armbar A long time favorite of south-east Asian cultures, it's basically just a straight armbar from that position, only you tuck the wrist into your armpit for even better leverage. Sometimes, I like to use this right away as I'm falling back for the armbar, as it automatically stabilizes the arm and applies pressure. It will make your opponent tap usually before you even flatten yourself out to start bridging the hips, so be sensitive with it in training.
Reverse triangle - Kimura Works best from the knee bent armbar (with your shin in their armpit instead of flat on their chest). Roll your hips over and slide the back calf underneath their head to establish a loose reverse triangle position, you can tighten that up if you want to, I usually don't. It's very important not to let go of the arm up to that point, because you need to be able to pin the arm down and give it some distance from the body (especially in gi, you can't let your opponent get a handhold on themselves, because it's alot of work to get them off) then slip your top hand over and apply the kimura.
Hope that was helpful.
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