I just got home from the store and while pulling out my TrustFire XP-E F23 from my pocket, it slipped and fell to the floor and now it won't work. It was only about 3 feet from my pocket to the hard linoleum floor. I thought the F23 would be a lot tougher than that. Man that really pisses me off. 
Oh well........
Any ideas what might have happened? I thought led's were almost indestructible especially this F23. Damn.....
I'd try tightening up the pill in the head end.
Then I'd try removing the switch and trying something conducting between the battery - and the body.
And, unlikely, try a different battery - if it is a protected 14500 it is possible the protection circuit got damaged.
Good luck and hoping it is something fixable.
Yes, one of my F23 died, but after more than 10 drops onto the concrete floor...
Mine destroyed the switch assembly (nor the led nor the driver)
Probably yours is simply the switch not fully screwed.
Try to diassembly the switch, clean the threads and reassembly the switch. OR you can make contact of the - pole of the batt to the threads to see if the problem is the switch or not.
Another failure can be the INDUCTOR in the driver board that has been desoldered due to the impact. Resolder it and again working.
the LED is the culprit. By the fact it came from a shock, I suggest to check first the solder point between the pill and the driver boad. Second, It might be any week soldered element, on the driver board itself, got loose. All this might be caused by the weight (inertia) of the battery, so, even a defective click switch could be possible.
Hmm, strange, my Tank007 TK-566-5 was dropped onto hard (duh) concrete from about 5 feet and nothing happened at all.
Read DX forums. This has happened to some owners, the driver destroys (probably desoldered inductor)
On mine, after 5 HARD drops the switch assembly broke forever..........
Before I forget, I was using a nimh aaa and even tried a freshly charged nimh aaa and still nothing. Ok, I just checked the switch and it works fine. I also tightened up the pill but still nothing. So I guess the problem is somewhere inside the pill. I've never taken one apart so what do I have to lose right? 
Probably is the inductor that is desoldered due to the inertia of the impact
Or the switch part, as in the mine
Can I just buy a new pill for my F23? It looks like a tiny P60 dropin.
Here are a few pics:
No you cant
Try to unsolder the driver an see if there is something loose and resolder it.
If not, try to make it direct drive and use always a 10440
slightly off topic, but i've seen videos of ppl putting fenix lights through destruction tests to see how well they hold up. it would be interesting (if someone has money to burn) to see how a select few budget lights hold up. You always see the battery life, lumen, lux etc. tests. wonder if anyone would run a light or two through the ringer so we all know what a good reliable work light would be (something that can take some abuse). maybe this is a stupid idea but it'd be interesting!
I know it is all dependant because QC on these lights is not top notch, but at least we may learn something from it :)
I'm willing to volunteer time if someone wants to volunteer the lights.
At least we know now that the Trustfire F23 doesn't hold up too well when dropped. :(