Another vote for the Streamlight Protac 1L-1AA
Compact enough for easy pocket carry
Runs on 1 single AA battery
350 lumens
Waterproof
Great when used as headlamp clipped to ball cap
Under $40
Easy "on" button for quick use
Bright/low/Strobe with each tap of button
Mine's going on 5 or 6 years now, very tough and reliable.