I, for one, am a flashlight junkie. You cannot go 5 feet in my home without tripping over a flashlight. Over the years I have tried just about every major brand of light that there is and have found that if you stick with obviously well built lights of any brand you'll probably be okay, and a well built light sticks out every time. That being said, I rank flashlights up there with guns and knives in my list of tools that are most important in a survival situation so I am unwilling to risk my safety on a cheap light. Personally, I use Surefire and Streamlight lights for everything. My EDC light is a Surefire E2D LED Defender, and I keep one of these lights with each of my handguns. Yes they are bloody expensive, and it is painful to buy them, but they are worth the money. The rest of my regular flashlights are from Streamlight. I keep a Sidewinder in each of my bags, and have several Stinger DS LED lights hanging on chargers with spare batteries on several walls in my place. I also use the Stinger day in and day out at work and it is a great light.
All that being said, I do not like keychain flashlights. I have owned several and they were all a disappointment. My last one was a Streamlight Nano, a nice light light, bright, well-made, but the on-off mechanism was incredibly frustrating. On the Nano, you twist the head to turn it on or off, and it had a bad habit of twisting in my pocket, quickly killing the batteries. I have now switched to carrying only small LED pushbutton type lights and am presently using this one from GearPods, https://www.gearpods.com/ProductDetails.asp?ProductCode=GFL-1
, they are cheap, work well, and what I really like is that it has a small lock to keep the light on rather than just have to hold the button all the time. I have now put these into all of my personal survival kits, hang one on each of my bags (from a zipper pull), and have them on all of my keychains.