Your favorite/most useful tool?

[Gabe]

It's going to break the rules, but I have three favorite tools, because they are so useful to me everyday:

1. 12" single-cut mill file with an adjustable handle. A big file is not only easier to hold, its length removes more metal in one pass and finishes the job quickly.

2. DeWalt 18V cordless XRP hammer-drill/driver. It's so handy to simply reach over and pick up the tool when I need it. It also has plenty of power for hard jobs like drilling through thick steel. (Only used hammer-drill once, but I was really glad that time!)

3. Custom folding pocket Allen key set with ball-end. I bought a folding ball-end set and switched the keys into my compact metal handled set. It really excels at driving screws at an angle, but easy to carry around. It is my most useful tool during build season.