I had the Sunwayman G20C failed on me while I was vacationing in Vietnam. It started to flicker and died… Later found out it was the tailcap; a wire was loose. Never dropped or did anything to it beside changing battery. Altho I got the tailcap replaced, I cannot trust it fully. Never took it on trips with me ever since.
I’m sure someone will tell me i’m wrong and tell me to get a REALLY reliable american-made flashlight. but my most reliable flashlight is probably my Emisar D4. dropped it a million times on concrete. fell into an oil pan at some point and has run on turbo till thermal step down for fuck knows how many times serving to illuminate an area. and the worst that happened to it was that the lens cracked at some point, which gave it an… interesting pattern when held under a lens.
other than that light I own a second world war pertrix flashlight which has served me well, It once died because the batteries inside it has gotten wet and exploded, but i was able to fully repair it using tinfoil and a little clear tape. this was on a multi-day hike and didn’t have another flashlight with me so that was a godsend. in reality though that flashlight is about as bright as a modern button cell LED (30 lumens maybe) with the e-10 incandescent, so not worth carrying at all. Tint is nice though :>
All of my flashlights are very reliable. No failures. I think Chinese manufacturing has reached near Japanese level quality.
My absolute most reliable flashlight would have to be my Surefire flashlights. They’re oldies… a U2 and a Kroma, featuring mechanical switches & lockouts. But because of low output, they get limited use.
But as for most reliable & usable EDC, I’d have to say my ZebraLight SC64c LE. ZL makes the best electronic switches. Right behind it is my Nitecore EC4GT, Jetbeam RRT-01 (original), Jetbeam U, and Skillhunt H03 RC. Jury is still out on the FW3A, as I’m wondering if the switch design will hold up for the long haul.
My Olight M18 Maverick has been a logger’s EDC for years—dropped, beaten around, loaned out and soaked in hydraulic oil countless times. Not much anodizing left on the old girl but she’s never let me down. Heck of a light.
"What is your current most reliable light? "
It's a 20-way tie among my 20 lights. None of them stand out as being more reliable than the others.
I kissed goodbye the world of unreliable lights in Oct, 2014, when I got my first real light, the Four-Sevens MMU-X3.
As long as I keep the usual contact areas clean, all is well.
There are some types of lights that are a bit more dirt sensitive, that will not be known as the Glock of flashlights.
If I had to go deep into a cave with only one light I would choose the Armytek Wizard Pro warm. I typically carry it as a backup light already without the headband. With the clip there are many optional ways to carry it and operate hands-free. With firefly 1 at 0.15 lumen all the way up to turbo 2 and everything in between you’ve got more than enough choices of output. 10 meters water proof. 10 meters drop proof. Magnet. It is cave ready.
My $6.00 tactical lights from aliexpress. I'm never afraid to use them, they get abused badly... drywall dust, cement, wet soil, the list goes on and on. I don't really know why they can take such a beating and maybe many of my lights can but this is the only one I don't feel guilty putting to work. Q8 is up there too.
Jetbeam Jet 1 MK. Or/and Astrolux AO1.
Always in pocket,
Serious use. Either My C8+ or Astrolux S41/S41S.
Or Imalent DN35/70.
They’ll do 98% of what you could want walking about.
From slight glow to 200+ Yards.
My eyes can’t see that far.
After that the world’s your oyster.
YLP Unicorn 1.0 with reflowed XPL HI V2 5D
I would have to say my Thorfire TG06s. It gets carried the most and gets knocked around in my pocket with keys. Hasn’t failed me yet.
Surefire G2 17670 w Malkoff drop in. Always comes on. M61LLW if I recall. Streamlight ProPoly 4AA Luxeon yes (gasp) Luxeon lol. Only 42 lumens yet very useful. Several others as well. 
Nitecore D10. I got the special edition one from Swissbianco (Magma), I’m using it pretty much every day since it came out (around 2008) and its’ been dead reliable. Great UI as well.
I think most will know a stock Convoy S2+ will be reliable.
My XM-L2 U4 0D with 8*7135 Convoy S2+ still working fine despite all the abuse. I stopped using them and it’s now my shower emergency light for 2 years going through daily shower rains still running tight and strong with no hints of water or fog.
But what comes 2nd to me is my main EDC Sofirn SP31 which has never failed me despite dropping on concrete floor shoulder height multiple times
I’ve had enough surprise failures with Lumintop, Fireflies, and Emisar that I wouldn’t want to rely on any of them even though some of them are my favorite lights. There are a lot of lights I would trust but if I had to pick only one it would be a Malkoff MD2 with M61L and twisty switch. It’s just so simple there ain’t much can go wrong.
Cave? My Armyteks. Dobermann, Partner, and one of those that shall not be named.
My Surefire 6P mod’s and a couple with Malkoff and PFlexPro drop in’s and all my Malkoff’s….
Surpringly my FW3A. I’ve opened it numerous times for modding (it’s got XP-L HI 5Ds) and similarly to djozz I wouldn’t rely on it unless this was the case. It’s never given me a problem… I guess I got lucky
Also, my 5600k sofirn C01 has been on my keys for a year now. That’s a reliable light in terms of both durability and battery life, especially with an energizer L92.
My “takes a licking and keeps on ticking” lights with beat to crap appearance are;
Olight s1
Zebralight sc62w
Four 7’s quark (aa)
ITP a3-eos (aaa)
Fenix Eo1 (aaa)
Fenix pd35vn TAC
Fenix HL60r headlamp
All have many hours of hard labor and lots of recharging.
None of my other lights have been through this much h€ll.
So far none of my Fenix, Zebralights, nitecores, 4sevens,and maglites have failed me. Ive had issues with an AAA clicky from coast. Threw it away.
6P bored for 18650 with Pflex Pro drop in and McClicky switch. Also has the beefy Lumens Factory SS bezel ring and Solarforce pocket clip. 