It is easy to mis-manage priorities, when it comes to preparing for emergencies. Certainly, if someone is kicking in your door, a firearm could come in handy, and if you're trapped in a car by your seat-belt, you might be very happy to have a pocket knife to cut yourself free. However, even during the course of normal life, lights are just handy. During emergencies, they often become vital. In this day of relatively inexpensive, high quality lights, there is no reason not to have a really good small light and a backup keychain light on your person every damn day.
SureFire has been probably the most recognized name in small "tactical" lights for years. SureFire lights are bright and sturdy. Unfortunately, they are also pricy and only use 123 cells. 123s are powerful and compact, but expensive. In the last few years, especially as LED technology has improved, many small, bright lights have been produced. Some of these use the less expensive, easily found AA batteries. One of my favorite of these is the Fenix line. Though they have expanded to include AAA and 123-sized lights, Fenix made its niche initially by making high quality lights that were less expensive than SureFire, but used AA cells. Couple a good 2 AA Fenix with some rechargeable AA lights, and you have a good daily carry light that's bright enough for emergencies, but inexpensive enough to buy for yourself and your loved ones.
Another option is rechargeable 123 cells. I have been carrying the LumaPower LM33 for some months now. This is a small single 123-battery light. Unlike some 123-powered lights (cough, SureFire, cough!), the LM33 can take rechargeable 123-sized batteries. Mine is currently running on 3.6V 880MAH Ultrafires that I charge with my tiny NanoCharger. For "tactical" use, a momentary press switch is preferred. The LM33 has a "reverse clicky" switch. The light comes on as the button pops back up. This is one of only two flaws I find with my LM33. The other is that its lower-powered mode is first. Fortunately, even the lower-powered mode is bright enough to use as a shooting light at close range.
At about twice the overall size of a tube of lip balm, the LM33 fits easily into a pocket. It has a luminescent ring at the top of the bezel, so after the light has been used, it can still be found for a while in the dark by the glowing ring. The LM33 also comes with an a luminescent clicky switch, if the user prefers that to the installed safety orange one. The LM33 comes with a small nylon holster and a lanyard that works for everyday use, but which will not stand up to truly hard duty.
At less than $30 shipped from Battery Junction, the LM33 is a small, useful light that can easily be accessorized with rechargeable batteries and a charger for about another $11. If you can live with the reverse clickly switch, I believe you will be very satisfied.
