We have seen several LED candle projects around. Their main purpose is to imitate real candle burning. Some of them generate flickering effect using pure code generated random number, other use sensor to sense environment like ambient light variation. It is up to you to judge which of them tend to be more realistic.
akafugu made very simple LED candle that runs on Attiny13A microcontroller. It drives single 1W LED. It can be turned on and of fusing single push button. Also there are two flickering modes – high and low intensity. Candle has a base shape of tealight and is powered by single CR2032 battery which ensures operation for about 40-50 hours.