The Little Glowing Friend (I named it after the ever-vigilant blue canary night light in a They Might Be Giants song) uses a single-chip microcontroller to drive 20 LEDs in a variety of patterns. The circuit is embedded in a clear resin casting, creating a lively, self-contained display. The light brick takes about 2 watts of power, and should last more than 10 years in continuous operation.
I gave away 24 of these in 2006; most have been on ever since, and there have been no reported failures. Electricity cost is about $1 a year, for 24×7 operation.