The list author says: "A comparison of small flashlights. Output is listed as brightness (in lumens (lm)), then an arrow (->) then runtime (in days (d) or hours (h)). Weights do not include batteries.
Regulated output means the output will stay essentially constant until the batteries are just about dead, and then drop quickly at the end. Unregulated means the light gets gradually dimmer (or even rather quickly sometimes) the more you use it.
Some of these come in a CR-123 flavour but I've left those off because it just gets to be too many things to compare. CR-123 batteries provide more brightness and/or runtime, work better in extreme temperatures, are heavier and more expensive, and are shorter and fatter (which is generally reflected in the flashlight as a whole). If all that sounds ok to you, you may want to check out lights such as the Fenix PD20 or the Quark Mini 123 as well.
Also not included are classics like Maglites, because they're just obsolete compared to new LED flashlights. For example, a 2AA mini maglite claims 12 lumens for 5.25 hours, which is far less than even the cheapest options on this list. They also put out splotchy uneven light patterns, and incandescent bulbs burn out much sooner than LEDs and are much more likely to break if handled roughly.
The list isn't in any particular order, because which flashlight is best depends entirely on what you want from it."
"Pros: cheap, lightweight, thin, easy to carry, long runtime Cons: Unregulated output. AAAA batteries aren't as easy to find. Bright enough for many typical needs but may not be bright enough for all uses. Other: Momentary or steady on. 10 lm->60h on 3 AAAA batteries. Weighs 1.1oz."
"Pros: Brighter than regular Stylus, AAA batteries should be easier to find Cons: Shorter runtime than stylus, thicker (but still fairly easy to carry). Unregulated output. Other: 24 lm->7.5h on 2 AAA batteries. Weighs 1.6oz"
"Pros: regulated output, multiple brightness levels offering extreme runtime or extreme brightness, special modes Cons: Heaviest option and one of the most expensive. A bit chunky to carry routinely but not terrible if you're expecting to need it. Other: 5 lm->100h to 180 lm->2.5h on 2 AA batteries. Also SOS and strobe modes. 5.9" long, weighs 2 oz."
"Pros: regulated output. Multiple modes offer longest runtime by far, as well as one of the brightest. Cons: expensive, relatively thick Other: 0.6 lm->53d to 177 lm->0.7h on 2 AAs, plus strobe and beacon modes. 5.9" long, weighs 2.2oz."
"Pros: Compact, lightweight, regulated, two brightness levels Cons: low mode gives less runtime and brightness than Stylus, more expensive Other: 8 lm->39h or 117 lm->1.5h on 1 AA. 3" long, weighs 1oz."
"Pros: extremely light and compact with good brightness. regulated output Cons: runtimes not as good as multi-cell models, expensive Other: 1.5 lm->67h to 65 lm->0.9h on 1 AAA, plus strobe, beacon, and SOS modes. 2.8" long, weighs 0.5oz."