Guitar Hero III
59 Achievements
1,000
Xbox 360
Half a Mill'
Score 500,000 on a song
10
How to unlock the Half a Mill' achievement in Guitar Hero III - Definitive Guide
This achievement is available on a handful of Expert songs including: "Holiday in Cambodia", "Cherub Rock", "Before I Forget", "Stricken", "Knights of Cydonia", "Number of the Beast", "One", "Take This Life", "The Way it Ends", "Through the Fire and Flames".
You have to be good to do this, so get some practice in.