The Aussie,
*If you use Oanda, the Aussie has a 2 pip spread (institutional rates) the pips are worth more (approx. 30- 50% more than the majors), so even though it seems to move less the dollar value of the moves are similar.
*It doesn't spike around or move as crazily as the majors (bounces around in 10/20 pip increments usually). It has a slower tempo of movement giving you more time to think and react (unlike cable).
*The intraday charts are "clean" ,I find not as noisy as other currencies. Technically speaking I often compare the intraday charts between currencies (especially tick charts) and the Aussie usually gives crisper chart signals to trade of. As a consequence I find I get less faked out from this pair.
* The BIG sharks probably play with the majors (EUR/USD, USD/JPY, GBP/USD, USD/CHF), so the small/mid sized sharks have it more to themselves = less heart ache??.
*AUS/USD = 4th or 5th most liquid pair (100 billion a day) so liquidity is absolutely not a problem whatever size transactions you have in mind.
*You don't have to trade it during the Asian session, although it usually has a good move in that time. I'm looking at it more and more during the "traditional hours" - european/us session.
*It's moves are tied to gold/metals (like the canadian etc.) so their is good volatility at the moment.
I think it's the ideal currency for a beginner. I'm also biased as I'm from downunder!