Reading the replies got me to wondering what tool that I use the most. It's not my favorite tool, or one that I particularly care for, but I have three of them in my toolbox, one in my clipboard, two in my truck box, three in my workshop and one outside with some yard tools.
The Steel Tape is my most used tool.
I wear out at least two of them a year, and always replace them with another as soon as possible. Right now, I'm liking the Kobalt brand tapes from Lowes. I wont' buy anything that says Stanley on it again, but they wont complain with all the money I've given them over the years. The three 25ft Kobalt tapes in my tool box all come out when I'm working. One with my saws where I'm cutting, one were I'm working and one in my tool belt.
After that, I would think my flat penciils are the most used. Maybe more. I always have at least one in my pocket and sometimes will have three or four.
Then it's a toss up between a pry bar, hammer, chisel, sheetrock knife, multi screwdriver and cordless drill.
Eddie