For EDC purposes I carry a Streamlight Microstream. I found mine for less than $15 and it's bomb proof. Portable, light weight, bright, good battery life, durable and inexpensive. Fits my EDC requirements flawlessly.
Specs:
CASE MATERIAL: Corrosion and water resistant, machined aircraft-grade aluminum alloy,Type II MIL-Spec anodize plating. Available in matte black finish.
DIMENSIONS: Length: 3.5 inches (90 mm) Body Diameter: 0.6 inches (15 mm)
WEIGHT: 1.04 oz. (29.7 grams) with battery
LENS: Unbreakable and scratch resistant polycarbonate lens
LIGHT SOURCE: 0.5 Watt High-Flux LED; 30,000 hours rated LED life
LIGHT OUTPUT: Up to 20 Lumens Typical
ON/OFF: Push Button Tail switch (with momentary on-off)
RUN TIME: Up to 1.5 hours of regulated runtime
BATTERY: One (1) AAA battery
FEATURES: Tailcap switch for momentary On/Off.
O-Ring Sealed, shock proof and drop tested construction
Water resistant per IPX4; in accordance with specification EN 60529:1992
High Strength Break Away safety lanyard.
Unbreakable pocket clip
I've found the battery life to be much longer than the official specs.