Started carying a simple Gerber folding knife. Has a 2.5 inch drop blade. Made a lanyard outta 550 chord and attach it to my Conterra radio harness or my FA fanny pack depending on what I'm doing.
It is not there necessarily for rope cutting but I have found it useful on occasion for cutting tape, christmas lights, string, First-aid-tape, repairing whipping, opening packages.
It is a standard edge, no serrations, as I find that more usefull all around. And I keep it uber sharp with a fine edge. Since it is not frequently used I find sharpening it after it has been used to be a reasonable hassle.