A cutter is how you open a cigar without chewing it. The cap is there to keep the wrapper from unravelling. Cut below it and you peel the cigar; cut nothing and you have no draw. Most people use a guillotine (straight cut), a v cut, or a punch.
Sharp matters more than brand. A dull blade crushes the head and pinches the bunch. Wipe it. Do not twist it through the cap like a dull apple corer.
Smoke Rings sells cutters in the shop. The wiki will not tell you which cigar to buy. See cutters for current listings.