The darce or brabo (with the gi) choke is a good option. Another thing I've started using in place of the darce when it's hard to lock it in tight (and if you're rolling with the gi) is kind of an inverted ezequiel choke. The set up is very similar to the darce, only you then reach inside your sleeve and go for the ezequiel rather than grabbing the biceps and locking in the darce. Another good option is to set up kind of like a half-nelson (whizzer the arm, hand on the back of his neck), and walk around through north-south to the other side. You end up with the arm trapped, and can set up various chokes, etc.