Keeping me away from my loved ones. :(
My experience with being trapped in a dream while someone next to me is snoring loudly has convinced me that if "the enemy" had me strapped to a chair and wanted information from me, they'd just have to make a loud noise over and over and over and over (at regular intervals). After a few hours, I would probably tell them anything to make it stop.
Harming a loved one in front of me while I am chained to a wall. That's one quick way to make me breakdown in tears, I suppose. However, forcing me to keep my head underwater is another way, too. Wait, why am I giving suggestions? O.o
Ouch . . . any form of torture, I suppose. Harming my family/friends in front of me seems like a very quick way to do it, although I bet I would succumb to pain alone.