Rolled with a couple people. While resting I watched a classmate showing a friend how to do a guillotine/kimura combo from guard, and was able to successfully use it later on when rolling. I was pretty pleased that I was able to pull it off, but I believe there was some luck involved.
Guillotine from Guard
* Pop up and get arm around the back of their neck
- blade of forearm should be on their throat
* Other hand should grab wrist
* Pull back, pulling neck down with pressure on back of head
Kimura from Guard (link)
* Works well if you nab it while they're fighting guillotine
* Grab their wrist with near arm and push it behind their back
* Once in position, lock it in with arm that was going for guillotine
* Push hips out, putting pressure on shoulder with elbow, and pushing their elbow back towards you