In the past couple of years my first aid kit has gotten very sparse. If you're being generous you can spout the party line about how when your knowledge base increases you will need less gear, but my medical knowledge base has always been rather considerable so honestly it is probably just complacency- I have yet to have a serious injury while hiking and I'm too lazy to carry a bunch of weight that I never need.
For day-hikes or weekenders I have a ziplock with some gauze, some Kling or Coban, a little triple-antibiotic ointment, Steri-Strips, and benzoin, as well as a couple of band-aids. My personal preference for tape is something like Hypafix or Mefix since it makes a handy blister-cover, too. I also carry diphenhydramine (Benadryl), ibuprofen (Motrin), and acetaminophen (Tylenol). The Benadryl is for envenomations and reactions to plants like poison ivy, and also helps sunburn a little. Heck, the Tylenol and Motrin will help you feel a little better after a sunburn, too, but mostly those are for soreness and the headaches that I get sometimes. (I usually carry an awful lot of Motrin, actually.) And note- you can take the Motrin and Tylenol at full strength simultaneously if you need to. They don't interact, but that can be a lot of NSAID at once so GI upset or ulcers are possible if you are predisposed.
For a day-hike or weekender I don't see much point in Loperamide or an antibiotic.
If you want to consider it part of the first aid kit, I also carry Hydropel and SportSlick. Likewise, my mini-Leatherman includes scissors and a tweezer, and duct-tape is all-purpose for almost any use where the Hypafix fails. Hand sanitizer is, well, a sanitizer, as is ethanol-based stove fuel.
But then I generally don't do activities that put me in great risk of large open wounds. I just hike, no mountaineering- at most a scramble now and then. If I got a big wound somehow I'd pack it with the gauze and bail out of the hike. Smaller wounds I might irrigate and Steri-Strip, and maybe bail out of the hike- but I can recognize a wound infection. Another point against suturing- I'm not sure where laymen could easily get their hands on the suture. It's not like WalMart stocks it. Or do they? Anyway, the single biggest cause of consumption of my first-aid supplies is the expiration date of those supplies. Practically speaking, if you pack something that is hard to get your hands on then it is a real pain to replace it when it expires every so often. Sticking to over-the-counter stuff is easiest.
Finally, Terry's experience notwithstanding I think that most people would have trouble doing a proper job of stitching themselves up in the back-country. Primarily you have to be sure the wound is clean first, which means irrigating, which hurts, etc. I doubt that anyone wants to haul a set of needle drivers around, though I guess that the pliers on a multi-tool would work. Steri-Strips and benzoin are a lot more user-friendly and tolerant of errors- and if you have a wound too big for that you should probably just pack it and bail. If you do want to carry suture carry a general-purpose nonabsorbable monofilament like nylon. Being nonabsorbable they will have to be removed later but most laymen can't distinguish an absorbable suture that's decaying from a wound infection, and they also can't manage subcutaneous sutures to avoid that problem. Monofilaments are less likely to sequester bacteria. The only convincing reason I can think of to carry an absorbable suture would be to tie off bleeding vessels in a really big wound before you close it, but even then laymen would be better served just to keep pressure on it for half an hour or so; I would not accidentally put a needle through a named vessel or nerve but can you honestly say the same?
For longer trips a lot of people on this forum advocate having your doctor give you a few narcotic pills in case you have to hike out on a sprained ankle and some antibiotics. In concept I agree with this, yet on all the longer hikes I've done I never seem to get around to picking some up. And I WORK at a hospital. I have packed loperamide on occasion, but you can get that over-the-counter. Otherwise I just take a bit more of similar stuff. For most hikes I can probably get out safely on a sprained ankle, even if it takes a while and I go hungry for a day or two. And it is hard (and expensive) to bring antibiotics for all eventualities. Your most likely malady is some sort of infectious gastroenteritis or infectious diarrhea, most of which have weeks-long incubations anyway and will thus hit you AFTER the hike, IIRC. The ones that have shorter incubations are viral so antibiotics aren't much use. If I were to bring a single broad-spectrum antibiotic a fluoroquinolone would be a good choice, but they are very expensive, especially for something you probably won't use and will have to throw out in a few months. On the cheaper side I think that something like Septra (aka Bactrim) would be decent, but you won't find a cheap single agent with great coverage. If you're doing truly long expeditions and want to cover the enteric culprits that people obsess about you'd need to bring some Flagyl. (I use the combination of fluoroquinolone/Flagyl a lot in my practice.)
Crazyglue- also a decent idea in concept, but I've never carried it. Realistically there's nothing it'll fix that a Steri-Strip and some benzoin won't. Also, I worry about the tube getting a leak- if you want surgical glue I'm pretty sure drug stores sell Dermabond capsules nowadays, don't they?
I have stopped carrying a large-bore needle. Really, what are the odds that I'm going to come across someone with a tension pneumothorax? I also don't carry a syringe for irrigation- I'm pretty sure that I could improvise something easily, and I'm a low-pressure believer anyway.
HAPE and HACE- there is no treatment other than descent. You may have heard of people taking Diamox or other diuretics but those are to speed acclimatization and to help control AMS symptoms, not HAPE or HACE. Descend. Fast. Hell, use your EPIRB if you have one because those are acutely life-threatening problems. Luckily I live at 7000 ft and have never had an altitude ailment.
I think that most people who are outdoorsy enough to come to this forum could improvise a splint.