L5030 LED Booster/Driver

This is really cool. You know those expensive, uber-duber, high efficiency, long life torches they always sell in Popular Mechanics or some gun mag? How do they do it?

With a chip like this.

The L5030 is a tiny SMT (surface mount technology) chip that drives LEDs using pulses. 

The idea is similar to that of a joule thief, using back EMF to boost voltage. The datasheet (here) has application circuits to show how to use it.

These sort of chips are easily available locally and open up all sorts of possibilities when it comes to efficiently running LEDs.