I rarely head out without  my Gerber Recon M flashlight.  It is handy to have especially if you live in a country where random nightly blackouts are the norm.  This little slug is made of type 3 hardened aluminum.  It has a single LED and a rotating bezel which changes the light filter.  Red, Green, Blue are available, and unfiltered White.  It is well sealed, and runs for hours and hours on a single AA battery.  I once left it on accidentally for at least 10 hours maybe more.  It was still on, any only slightly dimmer.  My estimation is 30-36 hours, but probably by 24 hours.  I could even be off and may have had the light on for much longer than 10 hours.  After that amount of time it may seem a bit dimmer when using the red or blue filter, which are already the darkest of the three filters.  The white unfiltered LED should still be powerful enough to be useful.

The clip is super tight.  The rotating bezel is also tight requiring good amount of force to rotate, and will not flip colors on you accidentally.  The light is activated by fully tightening the rear cap.  If you want to use it intermittently or flick on and off, then fully tighten the rear cap and back it off till it shuts off the light.  Now you can push on the rear cap and the light will stay on until you release pressure.

The end cap also has a large hole drilled in to thread paracord or whatever you like for a leash.  The Gerber Recon M 22-8017 and a Leatherman Skeletool CX make a great pair to have around.  The red filter is great for being discreet while providing a decent amount of illumination in your immediate surrounding.  The green filter is brighter but not blinding, and is good for signalling.  The blue filter lets you detect shiny objects, or liquids easily.  For the price (about 35-40 USD) it's been great, taken a beating, and looks like it will be kicking around with me for a long time.