For EDC on my person (as opposed to in my backpack, truck, etc) typically three, with jeans or shorts:
- Prometheus Beta-QRv2 on my keychain, MPHing an EN Al body for less weight with a Cu head for 3 mode function. (Eneloop Pro AAA)
- Olight S1 loose in a pocket. (RCR123A)
- Olight M1X Striker clipped inside pocket. (18650)
Of those three, the M1X is the one I typically reach for first when I need some light, because it's the most easily deployed and the brightest.
With slacks, I drop the M1X and just carry the S1 and Beta-QR. Pocket-clipped 18650s don't go well with slacks.
I never carry just one. Murphy's Law, when applied to flashlights, translates into if you're only carrying one and you really need it, that's when it will fail on you.