I'm guessing you mean getting the head of the cable stuck in the lever--my favorite tools are a variety of my dentist's castoff picks. The worst cases mean removing the lever, fixing it in a vise with soft jaws, and wiggling the pick through the cut-off stump of cable to push the head out from below. Most often found when generic cables have been used in Campag and Simplex levers.
David Feldman
Feldman's Bicycle Repair
Vancouver, WA
360-694-4228/503-998-7249