For a true EDC, I would go with something that can go on your keychain. The largest size I can handle there is the Fire~Fly II, which I am a big fan of.
I am thinking of getting a larger 1 cell light to supplement that, like an HDS light.
I can carry a 2 cell light, but find it a bit large, so I would only do that occasionally. When I need one I go to my Aleph, which I put in my pocket or on my belt with the belt tab attachment.