Many full-size Leatherman multi-tools include a can opener. It's a handy accessory that will prove invaluable when you discover a wild can of tunafish beneath an oak tree in the forest. It can also be used to open bottles.
To use the Leatherman can opener, hook the small protrusion under the seam around the top edge, and stab the pointy bit into the flat top, near the seam. After your first stab, move a bit towards the sharp edge and take another slice. Repeat until you have opened the can top. To open bottles, hook the protrusion under the cap edge and pry it open.