I feel like I've seen this tread before
I have carried a Leatherman Juice Cs4 for the past four years, and it's my baby. I've thought about replacing it but it's been through so much that I would have a hard time doing so. It's small, fits perfectly in the lighter pocket of my pants, and always gets the job done. I find myself mostly using the pliers/cutters and the knife most often, but the scissors come in handy for small stuff and there are also some screw driver bits that I tend to avoid using if possible.
I also carry a 5/32" allen key and a 7/16" driver bit, as those are the most common sized allens/bolt heads on our robot, as well as a dual tipped sharpie and a pen and pencil. And you won't catch me without my clipboard for notes (my short term memory is terrible) and a pit map.