I have a couple of simple thoughts on Survival Batteries and Flashlights.
I recommend trying to get all your lights with the same batteries. I have standardized to AA and AAA and CR2032 battery powered lights. I would like to have standardized to just AA batteries but there are just so many cool lights that are only available in AAA or the different button batteries. The most common button battery lights I have found usually use the CR2032 battery.
I only have LED Flash lights. I no longer have any Halogen or standard bulb lights for a couple of reasons. First LED lights put out a lot more light for the amount of battery power they use. Also LED bulbs are much more durable than most standard or Halogen bulbs. LED bulbs are not replaceable in most lights because they will outlast most of the cases. It is very rare to drop an LED flashlight and for the bulb to break. I have broken a couple in testing so it is possible but usually they will take a pretty good fall without breaking.
Most LED flashlights will use 3 batteries. They will take 3 AAA, 3 AA or 3 CR2032 batteries. Some of the bigger lights will take 3 D cells but they are rare.
I have bought about 50 AA and AAA flashlights. They can be very inexpensive and it is easy to put them in all your coats and bags.
I like having a flashlight around.
Headlamp Flashlights
No camping trip should occur without at least one headlamp light per person. I am a big fan of the lights with the little elastic band to go around your head. They make walking in the woods and around obstacles much safer. Most of these use the little button batteries like the cr2032 but some also use the AAA batteries. You can spend $40 or more on the rechargeable ones but I think this is a waste when for $40 you can purchase 15 to 40 of the inexpensive ones.
LED Lanterns
There are a lot of small LED lanterns available. I have used them for lighting tents and as nightlights for children. Many will have different levels of light output so you can use them as a room lighter or just as a night light. I have one that is both a standard flashlight on one end and a hanging standing lantern on the other.
Reading Lights
LED Flashlights designed as reading lights normally have a long neck and a clip to hold them to your book. These can be very handy clip on lights also.
Multiuse Flash Lights
I am always fond of tools that do more than one thing. I believe there is a lot of room for more originality in adding lights to many survival tools. Lights on knives, hatchets, saws, It is fairly common to find LED lights on Battery Jump boxes and some radios. This trend will go a lot further in the future.
More Carabiners for flashlights.
I would like to see more flashlights built with Carabiners as part of the light. These are really handy for clipping on the outside of your pack or belt loop and then giving you vision when you need it.
Baseball Cap Flashlights
The first time I saw one of these I thought what a piece of junk. After playing with one, they are pretty handy. They normally use two or three CR2032 batteries and clip onto the bill of your baseball hat.