Against some enemies in the Ice Cave in the WSC or PSX versions, such as Sorcerers and Mages, I'll become really desperate if I can't escape as soon as possible, and often a Thief is a party saver there. Thief's enhanced skills to run away from battles are also good to use if you're running low on healing, or if you need to save some strength (Marsh Cave and Earth Cave come to my mind quickly).