I like Brian's idea of asking what is actually used! For repairs, so far I've used duct tape and two safety pins. I of course have used the needle quite a bit for splinters and the dental floss daily for my teeth. I haven't yet sewn anything, though. The one time I needed to sew (big rip in pants in embarrassing location) I was on a dayhike without the sewing stuff (I had the needle, which resides with my first aid stuff, but no floss because I wasn't expecting to wash my teeth). I tried the duct tape, which preferred to stick to my skin instead of the pants (ouch!). I finally just tied my rain jacket around my waist, which hung down far enough to hide the rip.
The silnylon patch (self-sticking) goes with me because I have had my trekking pole tip slip out of its grommet and puncture the tent twice now. Both times were at home, but it would be rather scary if this happened during a trip! Duct tape doesn't stick too well to silnylon, I've found.
I once took along a McNett silnylon repair kit (from whence I got the self-sticking patch). It came in handy because I discovered a couple of spots on the tent that didn't get enough seam sealer. However, I should have tested the tent with a hose before leaving home! I now check tent (with garden hose), rain gear (in shower) and dry bags (in bathtub) every year. Trip preparation includes checking for weaknesses that might need mending (such as crotch seams in pants, lol).
Re duct tape on the trekking poles: I replace it every year, so no big deal. I recently threw away a 15-year-old roll, from which I'd used only about 10-12 feet--it had lost a lot of its stick!
For those who use the medical grade superglue--how well does it stick to silnylon?