Timer Boom is a free multi-purpose timer utility. The app consists of a single window that lets you set a timer. When the countdown clock reaches zero, one of many actions can be carried out. The default action is an alert, which will play an alarm sound. There are two sounds available. The more interesting actions let you stop iTunes playback, resume iTunes playback, sleep your Mac, and shut down your Mac. All of these alerts can be configured on the main window, where you use the up and down buttons to set the hours, minutes and seconds that you want for your time. When you are ready, all you need to do is click on "Set timer" and the countdown will start. It should be noted that you can only run one type of timer at the time. From the Preferences window, you can enable a separate window that shows a caricature of a boy holding a bomb with your timer on it. You can also enable a voice countdown when the timer reaches ten seconds.
In my testing, I tested both alert sounds and the "Stop iTunes" timer and they all worked fine.