Carillon is an open source OS X app, specifically for Hackintosh machines, that plays the classic "Chime" boot sound on startup that real Macs have. 

A new launch daemon will be added that triggers the sound, meaning, unlike most similar apps, this one runs much earlier during the boot process, even before the login screen appears. No crappy AppleScript solution that triggers when you're already on the Desktop, and no outdated PrefPane. 

It has currently been tested on OS X 10.8.2 and 10.8.5, but it should work on previous and future versions as well. Please report any issues you may have. 

No new icons or settings will be added. Reboot your system to enjoy. 

There's a demo video on YouTube.