Just about everything! I keep a few spools of it around in different colors. I look for 7-strand, think the last place I bought from was on ebay guy was in NC. I've used it for antennas, tarps, lanyards, bracelets, slings, belts, curtain hanging, covering handles, and even once or twice, tying things down!
I like to put paracord whipping on metal handles/grips, better when wet and cold. I have my hiking poles covered, they're quieter and more comfortable to hold, plus there's a few feet of cord if I need it. Also if you pull the inside strands out, you can use them for smaller string. Use the "gutted" shell for keeper cords on things like whistles, compasses, etc.
One of these days I'll have to post a video from my "camera zipline" made from 550 cord, a clothesline spacer and some hardware.
For even crazier applications, there's Amsteel Blue. The 1/8" cord is rated at 2,500 lbs. with almost no stretch. 100' of it weighs about 8 oz. and it floats! Not cheap, but in the right situation it's worth it.