I could see a number of neat sound options:
Harley Davidson Motorcycle
Ride of the Valkyries
Star Wars Theme
Theme from Jaws (both fun and a great warning!)
In reverse - the standard Beep, Beep, Beep that we all know and hate (but it gets your attention).
Blog That A-Ha Moment Larry Desjardin 11 comments Have you ever had an a-ha moment? Sure, you have. The Merriam-Webster dictionary defines it as "a moment of sudden realization, inspiration, insight, recognition, or ...