Life is full of compromises. Rather than forego carrying a flashlight based on size, there are small options easy to carry.
The LA Police Gear LP1 Tactical Pocket flashlight might not be as powerful as a larger light, but weighs under an ounce and a half (with batteries) and offers up to 80 lumens of light at the push of a button. It has three settings: high, low and strobe, which offer 3, 5 and 6 hours of operation respectively. Power comes from a single AAA battery (supplied with the light). It does all this at an MSRP under $15, too.
Operation is quite simple, with a pushbutton cap for instant activation. Push rapidly to cycle through the three settings, from high to low to strobe. There's no memory, though - when you push the button to turn the light back on after any length of time off, it activates to the next setting (i.e. if you have it on high, and shut it off, it goes to the low setting. Low goes to strobe, etc.)