No such thing as a best indicator Pat, other than one's eyes and whatever one's gifted with between one's ears. However, if there was a poll to discover the most used indicator to which traders attributed some sort of value, I'd guess it would be a basic moving average. Beyond that, it's all subjective - horses for courses etc.
The other key point here is it all depends on what you want an indicator to indicate. If you want to know the average range of prices over the previous x periods, I imagine most traders will agree that ATR does a pretty decent job. And all of them will agree its a whole heap better than MACD! However, implied in the thread title are the technical indicators that give a trader an edge - or contribute towards it at least - by way of gauging market direction and timing of their entry and exit. A number of them can do this, but the 'best' one is bound to be personal and governed by the way a trader integrates it into their trading strategy.
For swing and position traders who primarily use daily charts or longer, then there's a suite of
market indicators (as opposed to technical indicators) that may well be helpful. Of these, the
Bullish Percent Index would probably be my favourite. When I day traded the Dow, I became obsessed with $Tick, as that often appeared to be a leading market indicator that was much better at highlighting an overbought or oversold condition than say, a technical indicator like RSI. Ultimately though, you won't be surprised to learn that it wasn't the magic bullet I hoped it would be.
Tim.