Does anyone carry a tool on board for cutting wire rigging in an emergency (ie dismasting).
Just chiming in to note that dismasting is not the only event in which you may need to cut a piece of steel cable in a hurry.
Several years ago, on a prior boat, I was caught in a freak storm in which we were under motor in calm conditions and then hit with wall of wind exceeding 70 kts (Google "June 2012 derecho" for details on the storm). The wind blew the flaked and tied mainsail open from the boom like a balloon, knocking the boat on her side. Because the end of the boom was clipped to a steel cable hung from the backstay in lieu of a separate topping lift, releasing the mainsheet did nothing to dump wind from the sail. If I'd had a pair of wire cutters, I could have cut that steel cable to release the boom. As it was, I ended up slashing the sail itself to dump wind and right the boat. You do what needs to be done to save the boat and crew in a crisis, but in retrospect, a $300 pair of Felco cable cutters would have cost a lot less than a new mainsail.
In another example (though this one did not involve me personally), a friend was anchored out in a blow when another sailboat dragged its anchor and collided with his vessel. While the boats were moving separately in the waves, a lifeline stanchion on one boat wedged under and behind the upper lifeline of the other boat, effectively tying the two boats together, to the detriment of both hulls. Quick thinking and a cable cutter severed the fouled lifelines and saved both vessels from more significant damage.
I consider a pair of cable cutters essential safety equipment. Be sure to stow them where they are readily accessible. I am thinking of mounting mine on on the underside of a cockpit locker hatch.