It's not actually as stealthy as it looks here.
My old Sharpie ran out yesterday and I found an X-acto that somebody had dropped behind a shelf who knows how long ago, so I decided to combine the two. I cut off the front and back of the marker and the knurled grip of the X-acto was a perfect (tight) fit inside the head of the marker. I trimmed it down so the blade wouldn't stab too far into the plastic cap, yet left enough of the black head part so that the cap could get a grip on it.
I glued the knurled part of the knife into the black plastic part and then wrapped tape around the exposed area so the cap could hold on. I tried melting the tape a little bit, with some success, to get it to stay on the marker. Sharpie caps are usually held on just below the felt tip, although it's still the same black part.
So, yeah, just something fun that I took a half hour out of my day to do. The width of the marker makes it much more comfortable and easy to use and I no longer have to worry about caps. I use caps from old Bic pens on my other X-actos, but those are narrow so they become too sliced up to use after about a year.
Once another marker runs out, I might cut off the bottom half of it to slide over the exposed part of the knife here. It would just look like one extra-long Sharpie.