You really have to assess what it is that you might need to use a tool on. For example, some backpackers use some kind of pliers as a hot pot gripper. Fishermen always need some kind of similar tool for hooks. Cross country skiers always carry some kind of a tool with a posi-head driver to fit binding screws. I had to use some mini-visegrips to break into a stone cabin one time. Some backpackers might need a tool to repair a broken tent pole, or maybe to tighten up the screws on an adjustable trekking pole. Some photographers may need a similar tool to tighten screws on a tripod.
My multi-tool is relatively heavy, 2.4 oz., but it has pliers, wire cutter, knife blade, file, can opener, philips head driver, standard screw driver, an awl, a set screw tool, and a ruler in English and metric. As a result, I seldom carry it on a solo trip, and it generally goes with me on trips with others who need tools and never have them.