Another one-handed trick I learned from watching steel stud guys-
anvil-footed vise grips
steel stud guys carry about 6 or so of these, I just carry 2 small ones on steel stud jobs and they are great for holding 2 thin stud pieces tightly together while you screw them, or for hanging those awful recessed florescent cans in a stud bay, or as a third hand to hold up panels or whatever. I have found 100 uses for them and they're really great if you are have to fabricate mounts for lights, or if you are up a tall ladder and need the light to stay in some position contrary to gravity while you switch hands and grab your drill and a tek screw
