For everything from chopping food to cutting cord. You really only need one blade on a tool, though many come with two. Look for a blade with a locking mechanism so you don't risk cutting yourself. Also, if you're a peanut butter lover, pack along a Lexan plastic spreading knife so you don't have to gunk up the innards of your pocket tool. Scissors are imperative for making repairs to your tent, sleeping pad, clothes or anything else that requires a round patch.
Round patches are less prone to fraying or lifting than square ones.
Pliers tend to add a lot of weight to a tool, though, so decide for yourself whether they're really necessary. If you do, be sure your tool has one of these, as they're tough to improvise. Awls are used to punch holes in straps or belts. Since they're often short and stout, they also make good prying tools. Most tools have little engraved rulers on their sides, which is useful to measure tracks or insects.