I'm pretty much queer for surefire. I belive they are the toughest, most reliable, and well designed lights on the market. Peridod.
I've tried to EDC several over the years. Here's a few that I've used recently:
G2X Tactical (320 Lumens)
6px Tactical (320 Lumens)
E2D Defender Ultra (500 Lumens)
EB1 Backup (200 Lumens)
EB2 Backup (500 lumens)
Out of the ones i've used my favorite has been the EB2 Backup. It's very narrow, lightweight, easily carried in a pocket yet still provides an excellent output. I use the one with the tactical style tailcap. It has a low output of 5 lumens (half press) and 500 lumens on high (full press.) It runs off 2 CR123A batteries.
My wife currently uses the EB1 Backup. It's the same as the EB2 only it runs off 1 CR123A battery and has a 5/200 lumen output. She finds it easier to carry than the E2D that she previously carried. It is pretty small.
I carried a G2x and 6PX for a while. They have a larger diamiter head and body, less output and no pocket clip. They are however much more affordable. They're great lights no doubt but I found them somewhat less comfortable when carried in the pocket all day every day. One thing I highly reccomend is the Raven Concealment pocket clip (like $15). It fits any surefire with the 1" body such as the G2x and 6PX series. That's a must have when getting one of those lights.
I always use the twist style tailcaps. I'm not a huge fan of clicky style caps but some folks are. To each their own I guess.
Ike