The flashlight I use daily for work on the railroad

[B4Ctom1]

If you want a cool light that is not pokey/murder tipped like the others I reviewed, I suggest this sku.14027
http://www.dealextreme.com/details.dx/sku.14027
http://www.outlawperformance.com/uploads/sku_14027.jpg

Why?

features:
under $17 delivered (buy two)
sturdy clip (which can be removed)
thick rubber friction ring to assist the clip and aid in pocket retention
accepts a single 18650 or pair of CR123A
accepts emitter swaps using the common emitter module pattern

It comes with the Q5 emitter, but if you want to swap it for something more serious, read this:
http://230grain.com/showthread.php?p=82714

This is the very flashlight I use daily at work for federal locomotive inspections. I figure for under $17, if it is lost or stolen, or if it were to just die for no reason, I would not be too disappointed. I have already gotten more than $17 of use out of it.

[Fang]

Is there any output difference based on the battery it uses?

[B4Ctom1]

Is there any output difference based on the battery it uses?

These modules are internally regulated which means:

no difference at all between the 18650 and the two CR123's as far as brightness with the Q5 that came with it.

no difference with the R2 and R5 modules either in regards to battery voltage

Note: if you see my other post, I even screwed the back end of the pokey sku.20760 and used four CR123A's on this light. The voltage is too high for the Q5, but for the R5's 18v threshold it makes no difference. I even ran the R5'ed sku.20760 wit one CR123A, the result? just as bright. The only thing effected between one CR123A and four CR123A is runtime.

Attention: as usual I like to pass along this warning: when using rechargeable CR123A 3.6v batteries and trying to figure out how many volts they add up to you can still exceed the max voltage of an emitter module. It is more critical on xenon incandescents, but can still damage high power LED or their regulators. The reason is that a rechargeable CR123A 3.6v fresh off the charger can run 4.2v.

For example, I pulled hot 3.6v's off the charger and put them in my cousin's S&W xenon made for 3.0v's. If they would have been disposable 3.6v's everything would have been fine because the bulb could take the extra 1.2v's. But since they were fresh off the charger rechargeables, they were 4.2v and the extra 2.4v's was just a bit too much. A quick wink and it was out for good. I also did this to two of my own sportsmanguide xenons. No biggies, brought them back to life with these same drop in R2 and infrared LED modules.

So basically this: always check the max voltage range listed for your LED modules and always figure 3.6v recheargables at 4.2v for safety.

There are also 3.0v rechargeable CR123A, and the sku.1236 charger has a 3.0v/3.6v switch on the bottom. I prefer the 3.6V, and use 3.0v disposables in anything that can't handle.

You definitely need to check out my post here and scroll down for more developments on this flashlight:
http://230grain.com/showthread.php?t=67963

a hint.. what? what? WHAT?!?
http://www.outlawperformance.com/images/gunstuff/flashlight-mods/6-four_cell_sku20760-centers_sku14027-light.jpg