My first aid stash is quite good but not in an "I can doctor up and fix a broken leg" range.
I have tonnes of bandages - well, about 6 full packs of band aid type strips, quite a few sheets of steri-strips, about 15 large roller bandages and lots of packs of gauze, tubegauze, lint and rolls of tape etc. Lots of sterile wipes, tissues, etc. A few packs of gloves, a couple of bottles of sterile water (eyewash, or other needs). Plenty of cotton wool (a roll and a couple of packs of makeup remover pads that I keep for first aid). A couple of rolls of strapping tape (heavy duty physio stuff, not just elasotplast for sticking on plasters). Maybe half a dozen triangular bandages and a load of scout neckerchiefs too, and plenty of safety pins!
Hardware - decent scissors, and a shears to cut clothing. A couple of thermometers, decent tweezers (and my eyebrow ones can be used if needed too). I have a couple of cold packs (only 1 is a single use, and 3 are normally in the freezer) and maybe 20 re-useable heat packs (you click the button and they heat up, then after using, you boil them for 10 minutes and they go clear again to reuse when needed).
I have a small stock of painkillers, a couple of months of my asthma meds and maybe 3 weeks of DD's meds. I know there are other things that I need to replace (upset stomach, diarrhea etc). I do have arnica and savlon cream for bruises and cuts.
I sometimes contemplate getting something like a stethoscope and pressure cuff (I am trained in using them - not just for laughs), but I am not formally allowed to use them and can't really see a need at the moment for them. Splints can be made with wood from the shed or other strong items.
I have a small first aid kit for normal everyday use with a cold pack, band aids and a couple of wipes. A larger "mountain kit" which goes on longer events with a reasonable amount packed into it. And then a plastic "suitcase" style which I keep in my tent on camp with lots of spare bandages etc. All spare bits and bobs are kept in a larger plastic tub at home - although I am trying to reduce down what's in there as lots of it is not needed.