Currently my main torch is a Nite Core D10, which runs on a single AA Eneloop. Its brightness is continuously variable from 2 to 120 lumens, and it lasts for over 50 hours on dim. I recharge the battery every 6 months or so.

The light I use most often is the Countycomm Maratac AAA on my key ring. I've used this light almost daily for the past year, and have only replaced the battery once using standard Duracell AAA batteries. Having grown up in the era when the Mini-Mag was state of the art, it still amazes me how much light this tiny, lightweight flashlight puts out.

I also have a bunch of other LED flashlights from Fenix, most of which which I like, some not so much, plus the usual assortment of Photon's and similar, and a Pico.

But I like the Maratac AAA so much I bought several more and sprinkled them around my various kits.

I got extremely lucky and found a Surefire E1L Outdoorsman at an Unclaimed Baggage for 99 cents. Maglite's Solitaire are the old stand by.

I have to vote with the Quark 123.

That said my "most used" and "most carried" is the Flashlight app on my phone! (Not the one that puts the silly white circle on the screen but the one that leverages the camera's LED flash and lets you choose a brightness level.)

For a road trip last weekend I bought a new headlamp Princeton Tec Byte I was really impressed.

At $20 it costs a 1/3 less than my e+lite and its significantly brighter.

Its minimalist. Three settings. Red. Low white. High white.

The red was good for reading in a dark room but not so much for outdoor tasks like looking into a trunk. I used it to read in the back of a vehicle and the driver had no problems using the rear view mirror.
The low white is excellent for reading. The spread went accross a large book page. Also did well for basic walking through a dark house and looking for things in dark bags in a dark room.
The high white was outstanding for movement outside. I think my Tikka has a higher watt/lumen count but it is a larger unit.

Standard Disclaimers

I keep a 2xAA Coleman LED on my nightstand and have a similar one inside my SHTF bag. And 1 Inova Microlight on my keyring and a similar one on the outside of my SHTF bag.

In my company van I have a 4D Maglite, a 2xAA Maglite and an Energizer LED headlight. I also have various small 3xAAA "shorty" cheapo lights laying around everywhere so they're easy to get to.

The main one I use regularly would be the Inova on my keychain, because it's the closest one being in my pocket.

one of my "lessons learned" from the 04/05 hurricane season if you use a large 3D MagLight... cable tie a split ring (keyring)to your large lights so you can clip it to you (I carry my keys on an external nylon belt clip, and have replaced the spring clip of my Maxpedition cell pouch with a similar nylon belt clip ... I have a habit of setting it down and not remembering where it is...also added rings to my SureFire 6P and Nitrolon G2 towards the button end to give more purchase if used with a thumb forward grip using a pistol...

I must say, I do love my Illumina Ti (Model CA1-Ti) from Titanium Innovations. It lives on my keychain and takes a regular AAA battery. It is extremely bright and seemingly reliable so far...

It was a gift...my dad found it on eBay I think...but it's product info can be found here...
It can be found here if you are curious

(The usual disclaimer for the above link...)

I have a Princeton Tec Quad headlamp for night hiking and other hands-free tasks, a Princeton Tec Attitude LED light for general use, and a Maglite Solitaire on my keychain. I like the Princeton Tec brand because their lights are waterproof; actually, I used the Attitude once at the summer camp where I was working to try and find a pair of glasses a kid lost at the bottom of the lake (was not successful; a scuba diver ended up being called in and did find them).

Recently I've been using this light from DealExtreme.com. It was only $8 with free shipping. I believe the claimed rating is 110 lumens, but if so it must be at the emitter, not out-the-front. Still, it's a very bright light, especially considering it uses a single AAA battery. Even after carrying it for a few weeks and playing with it constantly, with the original battery it's still roughly as bright as my 3 D cell Mag-lite with fresh batteries! And of course it's about the size of my pinky finger and weighs about 1/100th as much as the Mag-Lite. Have I mentioned lately that Mag-lites really suck?