I have enough background and training in SAR and emergency medicine to where I can think of uses for several hundred pounds of emergency gear, but obviously I don't carry nearly that much.
It depends on your level of skills, your trip, and your group I suppose.
When I am serving as a "guide" in some formal sense I tend to carry a fairly big first aid kit, generally including such items as a 3'' ace bandage, oral airways, a suction/irrigation bulb syringe and catheter, scalpel, scissors, and significant dressing materials...
On personal trips, I probably will have three 4x4's, one gauze roll, some band-aids, and some pain meds.
My "big kit" focuses on airway maintenance, wound management, and would include certain critical drugs if I could buy them. Huge dressings and splints are easy to improvise, so they are the last things I would give space and weight to. I'm thinking about adding quickclot to this kit.
I always carry some multi-use tape, generally athletic tape or gorilla tape (the gorilla tape tends to go when I'm skiing, for it has many uses fixing ski equipment). I always carry some decent nylon cord, a sharp pocket knife, a lighter, and a whistle.
Personally, I am more inclined to carry real gear than "emergency gear" and try to never carry both redundantly. I cannot understand why people backpacking with a shelter and sleep system also carry a space blanket for example. I will err on the side of carrying more warm clothes and food if I am concerned that a trip might take longer than it should, rather than various devices intended to improvise with. I always take a decent headlamp with good batteries, and I leave the little squeeze-lights in the store.
The contents of my small first-aid kit all burns well, and with a lighter and knife added it's all I feel the need for most of the time. In the winter I often will carry a stove, even on a day trip, simply because it is the lightest way to carry water in a snowy environment. I also always carry some sort of shovel in the snow, since I think I can dig a better shelter than I could carry for the same weight (I have other reasons for the shovel as well...).
I seem to use the cord on a regular basis for various things, as well as the knife and the tape. I do end up using the whistle periodically when parties get spread out, and I can tell you it is one small, light object that SAR people hope you will have if they come looking for you, as it can make it much faster to find someone once they have reached earshot.
I have taken out everything that I've never needed to use.
If people really want carry more "emergency gear" I would advise the following:
If you really want an emergency signal device a PLB will be the most effective.
A small, light signal mirror actually does work pretty well to signal a helicopter under many conditions, especially for it's weight. Carry one if you want that ability.
Flares, smoke, and glow sticks are a waste of weight. You'd be better off carrying the weight in gear or food.
Fire building supplies should be balanced against your skill. That said, simply going from a lighter to waterproof matches can make things a lot easier.
If you carry some sort of emergency shelter, make sure it's actually big enough to be useful. This is also an area where skill can replace equipment.
Something you will use anyway is better than a something you will only use in an emergency (taking a sit pad on a day trip is an example, you might could get by without the pad if everything goes as planned, but if you have it you will use it, it would make a bivy much warmer, and it is a really great splinting resource).