Hmm, it's somewhat intimidating to post among such illustrious company, but here goes ...
1. Durability/Reliability - the "drop test" criteria is important, as are things like an incorporated spare bulb. Also, water-resistance, at a minimum, is also important.
2. Brightness - I still don't really understand candlepower comparisons, but as always, brighter is better (and yes, I agree that without quantification, this statement is rather useless)
3. Standard Parts - Mainly relates to batteries (the ability to use AA's being most desirable), but also includes bulbs to some degree
4. Battery life - I think 2 hours of useful light would be the bare minimum for me.
5. Size - Generally, jacket-pocketable is the upper limit for me, with pants-pocketable being more desirable.
I guess that's a reasonable listing of my "minimum" requirements. Based on my reading of the archived posts here, my flashlight tastes are rather crude. My daily carry is (don't laugh too hard) a MiniMag with NexStar bulb. I know it is not held in very high regard here, but I find that it fits my needs quite well. It has a lanyard hole that allows me to clip it to my keychain (my 2AA Legend does not), a spare bulb in the tailcap, and I really like the all metal body. After a year of carrying it around in my pocket, it's still in good shape, and I like its solid heft (particularly when I'm walking in a dark or deserted area). Also, since it has a smooth exterior finish, it slides easily in and out of my pockets, unlike the rubber coated Legend). The beam is plenty bright enough for lighting my path or illuminating even large enclosed areas. The battery life is quite good, and I really like the fact that it uses AAs (Hate throwing away alkaline or lithium batteries - I recharge my NIMH AAs every month or so, depending on usage).
So anyway, while I thoroughly enjoy reading about the various SureFires, PTs and UKEs discussed here (in particular I like the beam shot comparisons, such as those posted by MR Bulk), I haven't found anything to replace my trusty MiniMag. I recently got a Surge (man that thing is bright) but it's too big for daily carrying. I also have an old 4AA Energizer fluorescent/incandescent combo (I guess a precursor to the Arc White). I replaced the original bulb with an old one from my 3D Mag and it's pretty bright also (using NIMH batteries once again), but still too big for daily use. As I mentioned previously, the Brinkmann Legend is OK, but the rubberized grip and lack of attachment point make it less useful to me than the MiniMag. And the various LED lights I've picked up along the way have never quite been bright enough for me. So I guess in my rambling way, I'm trying to justify my MiniMag preference. Just seems like it's the light that best meets all of my "minimum requirements" - though I wouldn't be upset if someone pointed out a better alternative!
John